Xiaoping Gou

Lanzhou University, Kao-lan-hsien, Gansu Sheng, China

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Publications (23)101.9 Total impact

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    ABSTRACT: BAK1 was initially identified as a co-receptor of the brassinosteroid (BR) receptor, BRI1. Genetic analyses also revealed that BAK1 and its closest homolog BKK1 regulate a BR-independent cell-death control pathway. A double null mutant bak1 bkk1 displays a salicylic acid (SA)- and light-dependent cell-death phenotype even without pathogen invasion. Molecular mechanisms of the spontaneous cell death mediated by BAK1 and BKK1 remain elusive. Here we report our identification of a suppressor of bak1 bkk1 (sbb1-1). Genetic analyses indicated that the cell-death symptom in a weak double mutant, bak1-3 bkk1-1, was completely suppressed by the loss-of-function mutation of SBB1, which encodes a nucleoporin (NUP) 85-like protein. Genetic analyses also demonstrated that knocking-out three other NUPs individually from the SBB1-located sub-complex was also able to rescue the cell-death phenotype of bak1-3 bkk1-1. In addition, a DEAD box RNA helicase, DRH1, was identified in the same protein complex of SBB1 via a proteomic approach. The drh1 mutant can also rescue the cell-death symptom of bak1-3 bkk1-1. Further analyses indicated that the export of poly (A)(+) RNA was greatly blocked, resulting in accumulation of significant amount of mRNAs in the nuclei of the nup and drh1 mutants. Overexpression of a bacterial NahG gene to inactivate SA can rescue the cell-death symptom of bak1-3 bkk1-1. Meanwhile, mutants suppressing the cell death symptoms always showed greatly reduced SA contents. These results suggest that nucleocytoplasmic trafficking, especially for the molecules directly or indirectly involved in endogenous SA accumulation, is critical in BAK1 and BKK1-mediated cell-death control. This article is protected by copyright. All rights reserved.
    No preview · Article · Jan 2016 · The Plant Journal
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    ABSTRACT: Flowering plant sperm cells transcribe a divergent and complex complement of genes. To examine promoter function, we chose an isopentenyltransferase gene known as PzIPT1. This gene is highly selectively transcribed in one sperm cell morphotype (Svn) of Plumbago zeylanica, which preferentially fuses with the central cell during fertilization and is thus a founding cell of the primary endosperm. In transgenic Arabidopsis, PzIPT1 promoter displays activity in both sperm cells and upon progressive promoter truncation from the 5'-end results in a progressive decrease in reporter production, consistent with occurrence of multiple enhancer sites. Cytokinin-dependent protein binding (CPB) motifs are identified in the promoter sequence, which respond with stimulation by cytokinin. Expression of PzIPT1 promoter in sperm cells confers specificity independently of previously reported Germline Restrictive Silencer Factor (GRSF) binding sequence. Instead, a cis-acting regulatory region consisting of two duplicated 6-bp Male Gamete Selective Activation (MGSA) motifs occurs near the site of transcription initiation. Disruption of this sequence-specific site inactivates expression of a GFP reporter gene in sperm cells. Multiple copies of the MGSA motif fused with the minimal CaMV35S promoter elements confer reporter gene expression in sperm cells. Similar duplicated MGSA motifs are also identified from promoter sequences of sperm cell-expressed genes in Arabidopsis, suggesting selective activation is possibly a common mechanism for regulation of gene expression in sperm cells of flowering plants.
    Full-text · Article · Jan 2016 · Plant physiology
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    ABSTRACT: In plants, photoreceptors transfer light signals to phytochrome (phy)-interacting factors (PIFs), inducing PIFs rapid phosphorylation and degradation to promote photomorphogenesis. However, the phosphatase responsible for PIF dephosphorylation remains unknown. In this study, we identified a type-one protein phosphatase, TOPP4 that is essential for PIF5 protein stability in Arabidopsis. Compared to the wild type, the dominant-negative mutant, topp4-1, displayed reduced hypocotyl length and larger apical hook and cotyledon opening angle under red light. Overexpression of topp4-1 in the wild type led to defects that were similar to those in topp4-1 mutant. Red light induced phyB-dependent TOPP4 expression in hypocotyls. The topp4-1 mutation weakened the closed cotyledon angle of phyB-9 and phyA-211 phyB-9, while overexpression of TOPP4 significantly repressed the short hypocotyls of phyB-GFP seedlings, indicating that TOPP4 and phyB function in an antagonistic way during photomorphogenesis. Protein interaction assays and phosphorylation studies demonstrate that TOPP4 directly interacts with PIF5 and dephosphorylates it. Furthermore, TOPP4 inhibits red-light induced ubiquitination and degradation of PIF5. These findings demonstrate that dephosphorylation of PIF5 by TOPP4 inhibits its ubiquitin-mediated degradation during photomorphogenesis. These data outline a novel phytochrome signaling mechanism that TOPP4-mediated dephosphorylation of PIF5 attenuates phytochrome-dependent light responses.
    No preview · Article · Dec 2015 · Plant physiology
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    ABSTRACT: Receptor-like protein kinases (RLKs) are a large group of transmembrane proteins playing critical roles in cell-cell and cell-environment communications. Based on extracellular domain structures, RLKs were classified into more than 21 subfamilies, among which leucine-rich repeat RLKs (LRR-RLKs) belong to the largest subfamily in plants such as Arabidopsis and rice. In Arabidopsis, there are approximately 223 LRR-RLKs. Only about 60 of them have been functionally described. The majority of them need to be functionally determined. To systematically investigate their roles in regulating plant growth, development and stress adaptations, we generated promoter::GUS transgenic plants for all 223 LRR-RLKs and analyzed their detailed expression patterns at various developmental stages. These results provide valuable resources for the research community to functionally elucidate this large and essential signaling protein subfamily.
    Full-text · Article · Dec 2015 · Molecular Plant
  • Tao Shi · Ivan Dimitrov · Yinling Zhang · Frans E Tax · Jing Yi · Xiaoping Gou · Jia Li
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    ABSTRACT: Traits related to grain and reproductive organs in grass crops have been under continuous directional selection during domestication. Barley is one of the oldest domesticated crops in human history. Thus genes associated with the grain and reproductive organs in barley may show evidence of dramatic evolutionary change. To understand how artificial selection contributes to protein evolution of biased genes in different barley organs, we used Digital Gene Expression analysis of six barley organs (grain, pistil, anther, leaf, stem and root) to identify genes with biased expression in specific organs. Pairwise comparisons of orthologs between barley and Brachypodium distachyon, as well as between highland and lowland barley cultivars mutually indicated that grain and pistil biased genes show relatively higher protein evolutionary rates compared with the median of all orthologs and other organ biased genes. Lineage-specific protein evolutionary rates estimation showed similar patterns with elevated protein evolution in barley grain and pistil biased genes, yet protein sequences generally evolve much faster in the lowland barley cultivar. Further functional annotations revealed that some of these grain and pistil biased genes with rapid protein evolution are related to nutrient biosynthesis and cell cycle/division. Our analyses provide insights into how domestication differentially shaped the evolution of genes specific to different organs of a crop species, and implications for future functional studies of domestication genes.
    No preview · Article · Sep 2015 · Plant Molecular Biology
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    ABSTRACT: The formation of a zygote by the fusion of egg and sperm involves the two gametic transcriptomes. In flowering plants, the embryo sac embedded within the ovule contains the egg cell, whereas the pollen grain contains two sperm cells inside a supporting vegetative cell. The difficulties of collecting isolated gametes and consequent low recovery of RNA have restricted in-depth analysis of gametic transcriptomes in flowering plants. We isolated living egg cells, sperm cells and pollen vegetative cells from Oryza sativa (rice), and identified transcripts for approximately 36 000 genes by deep sequencing. The three transcriptomes are highly divergent, with about three-quarters of those genes differentially expressed in the different cell types. Distinctive expression profiles were observed for genes involved in chromatin conformation, including an unexpected expression in the sperm cell of genes associated with active chromatin. Furthermore, both the sperm cell and the pollen vegetative cell were deficient in expression of key RNAi components. Differences in gene expression were also observed for genes for hormonal signaling and cell cycle regulation. The egg cell and sperm cell transcriptomes reveal major differences in gene expression to be resolved in the zygote, including pathways affecting chromatin configuration, hormones and cell cycle. The sex-specific differences in the expression of RNAi components suggest that epigenetic silencing in the zygote might act predominantly through female-dependent pathways. More generally, this study provides a detailed gene expression landscape for flowering plant gametes, enabling the identification of specific gametic functions, and their contributions to zygote and seed development.
    No preview · Article · Sep 2013 · The Plant Journal
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    ABSTRACT: Genomic assay of sperm cell RNA provides insight into functional control, modes of regulation, and contributions of male gametes to double fertilization. Sperm cells of rice (Oryza sativa) were isolated from field-grown, disease-free plants and RNA was processed for use with the full-genome Affymetrix microarray. Comparison with Gene Expression Omnibus (GEO) reference arrays confirmed expressionally distinct gene profiles. A total of 10,732 distinct gene sequences were detected in sperm cells, of which 1668 were not expressed in pollen or seedlings. Pathways enriched in male germ cells included ubiquitin-mediated pathways, pathways involved in chromatin modeling including histones, histone modification and nonhistone epigenetic modification, and pathways related to RNAi and gene silencing. Genome-wide expression patterns in angiosperm sperm cells indicate common and divergent themes in the male germline that appear to be largely self-regulating through highly up-regulated chromatin modification pathways. A core of highly conserved genes appear common to all sperm cells, but evidence is still emerging that another class of genes have diverged in expression between monocots and dicots since their divergence. Sperm cell transcripts present at fusion may be transmitted through plasmogamy during double fertilization to effect immediate post-fertilization expression of early embryo and (or) endosperm development.
    Full-text · Article · Jun 2012 · New Phytologist
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    ABSTRACT: Brassinosteroids (BRs), a group of plant steroidal hormones, play critical roles in many aspects of plant growth and development. Previous studies showed that BRI1-mediated BR signaling regulates cell division and differentiation during Arabidopsis root development via interplaying with auxin and other phytohormones. Arabidopsis somatic embryogenesis receptor-like kinases (SERKs), as co-receptors of BRI1, were found to play a fundamental role in an early activation step of BR signaling pathway. Here we report a novel function of SERKs in regulating Arabidopsis root development. Genetic analyses indicated that SERKs control root growth mainly via a BR-independent pathway. Although BR signaling pathway is completely disrupted in the serk1 bak1 bkk1 triple mutant, the root growth of the triple mutant is much severely damaged than the BR deficiency or signaling null mutants. More detailed analyses indicated that the triple mutant exhibited drastically reduced expression of a number of genes critical to polar auxin transport, cell cycle, endodermis development and root meristem differentiation, which were not observed in null BR biosynthesis mutant cpd and null BR signaling mutant bri1-701.
    Full-text · Article · Apr 2012 · Journal of Integrative Plant Biology
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    ABSTRACT: The Arabidopsis thaliana somatic embryogenesis receptor kinases (SERKs) consist of five members, SERK1 to SERK5, of the leucine-rich repeat receptor-like kinase subfamily II (LRR-RLK II). SERK3 was named BRI1-Associated Receptor Kinase 1 (BAK1) due to its direct interaction with the brassinosteroid (BR) receptor BRI1 in vivo, while SERK4 has also been designated as BAK1-Like 1 (BKK1) for its functionally redundant role with BAK1. Here we provide genetic and biochemical evidence to demonstrate that SERKs are absolutely required for early steps in BR signaling. Overexpression of four of the five SERKs-SERK1, SERK2, SERK3/BAK1, and SERK4/BKK1-suppressed the phenotypes of an intermediate BRI1 mutant, bri1-5. Overexpression of the kinase-dead versions of these four genes in the bri1-5 background, on the other hand, resulted in typical dominant negative phenotypes, resembling those of null BRI1 mutants. We isolated and generated single, double, triple, and quadruple mutants and analyzed their phenotypes in detail. While the quadruple mutant is embryo-lethal, the serk1 bak1 bkk1 triple null mutant exhibits an extreme de-etiolated phenotype similar to a null bri1 mutant. While overexpression of BRI1 can drastically increase hypocotyl growth of wild-type plants, overexpression of BRI1 does not alter hypocotyl growth of the serk1 bak1 bkk1 triple mutant. Biochemical analysis indicated that the phosphorylation level of BRI1 in serk1 bak1 bkk1 is incapable of sensing exogenously applied BR. As a result, the unphosphorylated level of BES1 has lost its sensitivity to the BR treatment in the triple mutant, indicating that the BR signaling pathway has been completely abolished in the triple mutant. These data clearly demonstrate that SERKs are essential to the early events of BR signaling.
    Full-text · Article · Jan 2012 · PLoS Genetics
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    Jia Li · Junbo Du · Kai He · Xiaoping Gou
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    ABSTRACT: Arabidopsis contains at least 223 leucine-rich repeat receptor-like pro-tein kinases (LRR-RLKs). The somatic embryogenesis receptor kinases (SERKs) form a small subfamily of the LRR-RLK family. The BRI1-associated receptor kinase (BAK1 or SERK3) was identified as a co-receptor of the brassinosteroid (BR) receptor BRI1. Loss-of-function genetic analysis indicates that BAK1 and its closest paralog BKK1 are independently involved in BRI1-mediated BR signaling and cell-death control signaling pathways. More recently, BAK1 has been identified as a co-receptor interacting with a number of distinct ligand-binding RLKs to regulate multiple signaling pathways. This chapter will mainly discuss how BAK1 and BKK1 were identified as key regulators in controlling cell death, and the possible mechanisms involved in this process.
    Full-text · Article · Jan 2012
  • Xiaoping Gou · Jia Li
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    ABSTRACT: Insertional mutagenesis is one of the most effective approaches to determine the function of plant genes. However, due to genetic redundancy, loss-of-function mutations often fail to reveal the function of a member of gene families. Activation tagging is a powerful gain-of-function approach to reveal the functions of genes, especially those with high sequence similarity recalcitrant to loss-of-function genetic analyses. Activation tagging randomly inserts a T-DNA fragment containing engineered four copies of enhancer element into a plant genome to activate transcription of flanking genes. We recently generated a new binary vector, pBASTA-AT2, which has been efficiently used to discover genes involved in BR biosynthesis, metabolism, and signal transduction. Compared to pSKI015, a commonly used activation tagging vector, pBASTA-AT2, contains a smaller size of T-DNA and a bigger number of unique restriction sites within the T-DNA region, making cloning of the flanking sequence a lot easier. Our analysis indicated that pBASTA-AT2 gives dramatically improved transformation efficiency relative to pSKI015. In this article, detailed information about this activation tagging vector and the protocol for its application are provided. Three recommended gene cloning approaches based on the use of pBASTA-AT2, including inverse PCR, thermal asymmetric interlaced PCR, and adaptor ligation-mediated PCR, are described to identify T-DNA insertion sites after selection of activation-tagged mutant plants.
    No preview · Article · Jan 2012 · Methods in molecular biology (Clifton, N.J.)
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    Jiaxing An · Zhongxin Guo · Xiaoping Gou · Jia Li
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    ABSTRACT: Brassinosteroids (BRs) are a group of major phytohormones playing critical roles in plant growth and development. Within the last two decades, key events of BR biosynthesis and signal transduction have been gradually elucidated. The detailed molecular mechanisms controlling bioactive levels of BRs, however, are not fully understood. TCP1 is a member of class II TCP proteins in Arabidopsis thaliana. The role of TCP1 in BR biosynthesis was discovered by an activation tagging analysis aiming to screen for genetic suppressors of an intermediate allele named bri1-5 of the BR receptor gene BRI1. Overexpression of TCP1 partially suppresses the defective phenotypes of bri1-5 via direct up-regulation of DWF4, one of the target genes of TCP1.
    Preview · Article · Aug 2011 · Plant signaling & behavior
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    ABSTRACT: The promoter sequence of sperm-expressed gene, PzIPT isolated from the S(vn) (sperm associated with the vegetative nucleus) of Plumbago zeylanica, was fused to a green fluorescent protein (GFP) reporter sequence and transformed into Arabidopsis thaliana to better visualize the live behavior of angiosperm sperm cells. Angiosperm sperm cells are not independently motile, migrating in a unique cell-within-a-cell configuration within the pollen tube. Sperm cells occur in association with the vegetative nucleus forming a male germ unit (MGU). In Arabidopsis, GFP was expressed equally in both sperm cells and was observed using a spinning disk confocal microscope, which allowed long duration observation of cells without bleaching or visible laser radiation damage. Pollen activation is reflected by conspicuous movement of sperm and pollen cytoplasm. Upon pollen germination, sperm cells enter the forming tube and become oriented, typically with a sperm cytoplasmic projection leading the sperm cells in the MGU, which remains intact throughout normal pollen tube elongation. Maturational changes, including vacuolization, general rounding and entry into G2, were observed during in vitro culture. When MGUs were experimentally disrupted by mild temperature elevation, sperm cells no longer tracked the growth of the tube and separated from the MGU, providing critical direct evidence that the MGU is a functional unit required for sperm transmission.
    No preview · Article · Nov 2010 · Planta
  • Hui Yang · Xiaoping Gou · Kai He · Dehui Xi · Junbo Du · Honghui Lin · Jia Li
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    ABSTRACT: BAK1 and BKK1 are receptor-like protein kinases (RLKs) involved in brassinosteroid signal transduction and plant resistance to bacteria and fungi. Here we report that loss-of-function mutants of BAK1 or BKK1 in Col-0 showed enhanced susceptibility to Turnip crinkle virus (TCV) infection. Cell death and chlorosis occurred much earlier in bak1-4 and bkk1-1 mutants than in wild-type plants, suggesting an important role of BAK1 and BKK1 in controlling cell death associated with TCV infection. The bak1-4 and bkk1-1 mutants showed the elevated transcription levels of pathogenesis genes, such as PR1, PR2, PR5, PDF1.2. Enhanced expression of these genes, however, failed to resist the transport of TCV virus. At 9days postinoculation, TCV levels were the highest in the systemic leaves of bak1-4, but were undetected in BAK1 or BKK1 overexpressing plants. These results signify that both BAK1 and BKK1 are important components in controlling TCV infection in Arabidopsis plants. Keywords Turnip crinkle virus (TCV)-Susceptible-Cell death-BAK1-BKK1
    No preview · Article · May 2010 · European Journal of Plant Pathology
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    Scott D Russell · Xiaoping Gou · Xiaoping Wei · Tong Yuan
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    ABSTRACT: Flowering plant reproduction is characterized by double fertilization, in which two diminutive brother sperm cells initiate embryo and endosperm. The role of the male gamete, although studied structurally for over a century at various levels, is still being explored on a molecular and cellular level. The potential of the male to influence development has been historically underestimated and the reasons for this are obvious: limitations provided by maternal imprinting, the much greater cellular volume of female gametes and the general paucity of paternal effects. However, as more is known about molecular expression of chromatin-modifying proteins, ubiquitin pathway proteins and transcription factors in sperm cells, as well as their ability to achieve effect by intaglio expression, passing transcripts directly into translation, the role of the male is likely to expand. Much of the expression in the male germline that appears to be distinct from patterns of pollen vegetative cell expression may be the result of chromosomal level regulation of transcription.
    Preview · Article · Apr 2010 · Biochemical Society Transactions
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    ABSTRACT: Brassinosteroids (BRs) are essential phytohormones regulating normal plant growth and development. TCP1, a gene thought to be involved in floral organ symmetric control, was identified as a genetic suppressor of a weak BR receptor mutant, bri1-5, in an activation-tagging genetic screen. TCP1 encodes a putative transcription factor possessing a basic helix-loop-helix domain. The dominant allele of TCP1, tcp1-1D, suppresses the defective phenotypes of bri1-5. Overexpression of a dominant-negative form of TCP1, TCP1-SRDX, with a 12-amino acid repressor sequence fused to TCP1 at its C terminus, results in dwarfed plants resembling BR-deficient or insensitive mutants. The defective phenotypes can be rescued by exogenously applied brassinolide but cannot be recovered by auxins, gibberellins, or cytokinins. BR profile assay (quantitative analysis of BR biosynthetic intermediates) strongly suggests that TCP1 expression level positively coordinates with the function of DWARF4 (DWF4), a key enzyme in BR biosynthesis. Real-time RT-PCR analysis further demonstrated that TCP1 regulates the transcription levels of DWF4, and chromatin immunoprecipitation experiments showed that TCP1 indeed interacts with the DWF4 promoter. Confocal microscopy indicated that TCP1 is mainly confined to the nucleus. The expression of TCP1 appears to be regulated by BR levels. These studies demonstrate another level of regulation through which BRs mediate plant growth and development.
    Full-text · Article · Apr 2010 · The Plant Cell
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    Xiaoping Gou · Kai He · Hui Yang · Tong Yuan · Honghui Lin · Steven D Clouse · Jia Li
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    ABSTRACT: Transmembrane receptor kinases play critical roles in both animal and plant signaling pathways regulating growth, development, differentiation, cell death, and pathogenic defense responses. In Arabidopsis thaliana, there are at least 223 Leucine-rich repeat receptor-like kinases (LRR-RLKs), representing one of the largest protein families. Although functional roles for a handful of LRR-RLKs have been revealed, the functions of the majority of members in this protein family have not been elucidated. As a resource for the in-depth analysis of this important protein family, the complementary DNA sequences (cDNAs) of 194 LRR-RLKs were cloned into the Gateway donor vector pDONR/Zeo and analyzed by DNA sequencing. Among them, 157 clones showed sequences identical to the predictions in the Arabidopsis sequence resource, TAIR8. The other 37 cDNAs showed gene structures distinct from the predictions of TAIR8, which was mainly caused by alternative splicing of pre-mRNA. Most of the genes have been further cloned into Gateway destination vectors with GFP or FLAG epitope tags and have been transformed into Arabidopsis for in planta functional analysis. All clones from this study have been submitted to the Arabidopsis Biological Resource Center (ABRC) at Ohio State University for full accessibility by the Arabidopsis research community. Most of the Arabidopsis LRR-RLK genes have been isolated and the sequence analysis showed a number of alternatively spliced variants. The generated resources, including cDNA entry clones, expression constructs and transgenic plants, will facilitate further functional analysis of the members of this important gene family.
    Preview · Article · Jan 2010 · BMC Genomics
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    Xiaoping Gou · Tong Yuan · Xiaoping Wei · Scott D Russell
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    ABSTRACT: Plumbago zeylanica produces cytoplasmically dimorphic sperm cells that target the egg and central cell during fertilization. In mature pollen, the larger sperm cell contains numerous mitochondria, is associated with the vegetative nucleus (S(vn)), and fuses preferentially with the central cell, forming endosperm. The other, plastid-enriched sperm cell (S(ua)) fuses with the egg cell, forming the zygote and embryo. Sperm expressed genes were investigated using ESTs produced from each sperm type; differential expression was validated through suppression subtractive hybridization, custom microarrays, real-time RT-PCR and in situ hybridization. The expression profiles of dimorphic sperm cells reflect a diverse and broad complement of genes, including high proportions of conserved and unknown genes, as well as distinct patterns of expression. A number of genes were highly up-regulated in the male germ line, including some genes that were differentially expressed in either the S(ua) or the S(vn). Differentially up-regulated genes in the egg-targeted S(ua) showed increased expression in transcription and translation categories, whereas the central cell-targeted S(vn) displayed expanded expression in the hormone biosynthesis category. Interestingly, the up-regulated genes expressed in the sperm cells appeared to reflect the expected post-fusion profiles of the future embryo and endosperm. As sperm cytoplasm is known to be transmitted during fertilization in this plant, sperm-contributed mRNAs are probably transported during fertilization, which could influence early embryo and endosperm development.
    Full-text · Article · Jun 2009 · The Plant Journal
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    Kai He · Xiaoping Gou · Rebecca A Powell · Hui Yang · Tong Yuan · Zhongxin Guo · Jia Li
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    ABSTRACT: BAK1 and BKK1 are two functionally redundant leucine-rich repeat receptor-like protein kinases (LRR-RLKs) involved in brassinosteroid signal transduction by their direct interactions with the BR receptor, BRI1. Recent studies from our group and others indicated that the two RLKs also play critical roles in regulating pathogen-related and pathogen-unrelated cell-death controls. Genetic data suggest that the two kinases are essential for plant survival because the double mutants show spontaneous cell-death and seedling lethality phenotypes. Physiological analyses further suggest that the cell-death of the double mutant is triggered by the light, as dark-grown seedlings do not show any cell-death symptoms. These observations indicate that BAK1 and BKK1 regulate a novel signaling pathway to detoxify or to limit the production of a yet unknown toxin/toxins produced by plants under light conditions.
    Full-text · Article · Nov 2008 · Plant signaling & behavior
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    ABSTRACT: Brassinosteroids (BRs) are phytosteroid hormones controlling various physiological processes critical for normal growth and development. BRs are perceived by a protein complex containing two transmembrane receptor kinases, BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) [1-3]. BRI1 null mutants exhibit a dwarfed stature with epinastic leaves, delayed senescence, reduced male fertility, and altered light responses. BAK1 null mutants, however, only show a subtle phenotype, suggesting that functionally redundant proteins might be present in the Arabidopsis genome. Here we report that BAK1-LIKE 1 (BKK1) functions redundantly with BAK1 in regulating BR signaling. Surprisingly, rather than the expected bri1-like phenotype, bak1 bkk1 double mutants exhibit a seedling-lethality phenotype due to constitutive defense-gene expression, callose deposition, reactive oxygen species (ROS) accumulation, and spontaneous cell death even under sterile growing conditions. Our detailed analyses demonstrate that BAK1 and BKK1 have dual physiological roles: positively regulating a BR-dependent plant growth pathway, and negatively regulating a BR-independent cell-death pathway. Both BR signaling and developmentally controlled cell death are critical to optimal plant growth and development, but the mechanisms regulating early events in these pathways are poorly understood. This study provides novel insights into the initiation and crosstalk of the two signaling cascades.
    Full-text · Article · Aug 2007 · Current Biology

Publication Stats

552 Citations
101.90 Total Impact Points

Institutions

  • 2012-2016
    • Lanzhou University
      • School of Life Science
      Kao-lan-hsien, Gansu Sheng, China
  • 2006-2012
    • University of Oklahoma
      • Department of Microbiology and Plant Biology
      Norman, Oklahoma, United States