[Show abstract][Hide abstract] ABSTRACT: In this paper we focus our attention on RIXI, a member of the XIP type xylanase inhibitor proteins in rice. RIXI-overexpression transgenic lines were generated by expressing the RIXI gene under the control of auliflower mosaic virus 35S promoter. In comparison with the wild-type (WT) plants, the transgenic plants had significantly increased levels of RIXI and showed resistance to Magnaporthe oryzae. Transgenic plants also contained higher levels of H2O2 and had larger changes in catalase and superoxide dismutase activities than the WT plants. The results showed that the increase in RIXI expression was accompanied by the up-regulation of pathogenesis-related genes and genes related to the jasmonate signaling pathway. To clarify the expression pattern of RIXI, a ProRIXI: GUS vector was constructed and transgenic rice lines were obtained. GUS staining results suggested that the RIXI gene possessed distinctive, tissue-specific and grow stage-specific expression patterns in rice. This is the first report on the expression patterns of rice xylanase inhibitors and our results provide direct evidence, at the plant level, that xylanase inhibitors are involved in plant defense against fungal pathogens.
No preview · Article · Dec 2014 · Plant Cell Tissue and Organ Culture
[Show abstract][Hide abstract] ABSTRACT: Members of the ATP Binding Cassette B/Multidrug-resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily were shown to function primarily in auxin transport. However, none of rice ABCB transporters have been functionally characterized. Here, we describe that a knock-down of OsABCB14 confers decreased auxin concentrations and polar auxin transport rates, conferring insensitivity to 2,4-D and IAA. OsABCB14 displays enhanced specific auxin influx activity in yeast and protoplasts prepared from rice knock-down alleles. OsABCB14 is localized at the plasma membrane pointing to an important directionality under physiological conditions. osabcb14 mutants were surprisingly found to be insensitive to iron deficiency treatment (–Fe). Their Fe concentration is higher and up-regulation of Fe-deficiency responsive genes is lower in osabcb14 mutants than in wild type rice, Nipponbare (NIP). Taken together, our results strongly support the role of OsABCB14 as an auxin influx transporter involved in iron homeostasis. The functional characterization of OsABCB14 provides insights in monocot auxin transport and its relationship to Fe nutrition.This article is protected by copyright. All rights reserved.
Full-text · Article · May 2014 · The Plant Journal
[Show abstract][Hide abstract] ABSTRACT: N-glycosylation is a major modification of glycoproteins in eukaryotic cells. In Arabidopsis, great progress has been made in functional analysis of N-glycan production; however, there are few studies in monocotyledons. Here, we characterized a rice (Oryza sativa L.) osmogs mutant with shortened roots and isolated a gene coding a putative mannosyl-oligosaccharide glucosidase (OsMOGS), an ortholog of α-glucosidase I in Arabidopsis, which trims the terminal glucosyl residue of the oligosaccharide chain of nascent peptides in the endoplasmic reticulum (ER). OsMOGS is strongly expressed in rapidly cell-dividing tissues and OsMOGS protein is localized in the ER. Mutation of OsMOGS entirely blocked N-glycan maturation and inhibited high-mannose N-glycan formation. The osmogs mutant exhibited severe defects in root cell division and elongation, resulting in a short-root phenotype. In addition, osmogs plants had impaired root hair formation and elongation, and reduced root epidemic cell wall thickness due to decreased cellulose synthesis. Further analysis showed that auxin content and polar transport in osmogs roots were reduced due to incomplete N-glycosylation of the B subfamily of ATP-binding cassette transporter proteins (ABCBs). Our results demonstrate that involvement of OsMOGS in N-glycan formation is required for auxin-mediated root development in rice. This article is protected by copyright. All rights reserved.
Full-text · Article · Mar 2014 · The Plant Journal
[Show abstract][Hide abstract] ABSTRACT: Salt stress often induces declination of net photosynthetic rate (Pn), partially resulted from Rubisco degradation. The chloroplast protrusions (CPs) is one of the pathways of Rubisco exclusion from chloroplasts. To explore the relationship between the Rubisco contents and CPs under salt stress, Pn, maximum photochemical efficiency of PSII (Fv/Fm), carboxylation efficiency (CE) and concentration of Rubisco, number of CPs and Rubisco-containing Body (RCBs) were investigated with two differently salt-responding varieties in this experiment. We observed that 150 mM salt treatment resulted in not only significant decrease in Pn, CE and Rubisco content, but also obvious increase in the number of CPs and RCBs in salt-sensitive variety. Under salt stress formation of CPs resulted in production of much more RCBs, which could immigrate into and combine with vacuole. It may be a kind of important mechanism for rapid degradation of Rubisco under salt stress. Our conclusion provides a new sight for how Rubisco can be fast degraded under salt stress.
Full-text · Article · Nov 2013 · Plant Physiology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Background:
Xylanases have attracted considerable interest in recent years owing to their various applications in industry and agriculture. The use of transgenic plants to produce xylanases is a less expensive alternative to biotechnological programmes. The aim of this study was to elucidate whether introducing a foreign xylanase gene ATX into rice had any adverse effect on plant growth and development.
A recombinant xylanase gene ATX was introduced into rice variety Zhonghua 11 through Agrobacterium-mediated transformation. The T₂ generation of transgenic rice was compared with the control (non-transgenic plants). Exogenous xylanase gene ATX was expressed in rice, and all examined transgenic lines exhibited xylanase activity. The transgenic lines (T₂, 'X1-3' and 'X2-5') appeared to grow and develop normally. There were no differences in net photosynthetic rate between transgenic rice lines ('X1-3' and 'X2-5') and wild type (WT) rice plants at the heading/flowering stage. Xylanases are key enzymes in the degradation of plant cell walls. Cell wall composition analysis showed that that there were no changes in cell wall polysaccharides in the root apex but some alterations in leaves in transgenic rice plants. The results also showed that the expression of exogenous xylanase gene ATX in rice would increase the expression of endogenous xylanase inhibitor gene RIXI, which could play a role in plant defence. Thus the stress resistance of transgenic rice plants might be improved.
Exogenous xylanase gene ATX could be successfully expressed in rice, and the exogenous protein had no apparent harmful effects on growth and development in transgenic rice plants.
No preview · Article · Jan 2013 · Journal of the Science of Food and Agriculture
[Show abstract][Hide abstract] ABSTRACT: Mi-2 protein, the central component of the NuRD nucleosome remodeling and histone deacetylase complex, plays a role in transcriptional repression in animals. Mi-2-like genes have been reported in Arabidopsis, though their function in monocots remains largely unknown. In the present study, a rice Mi-2-like gene, OsCHR4 (Oryza sativa Chromatin Remodeling 4, LOC_Os07g03450), was cloned from a rice mutant with adaxial albino leaves. The Oschr4 mutant exhibited defective chloroplasts in adaxial mesophyll, but not in abaxial mesophyll. Ultrastructural observations indicated that proplastid growth and/or thylakoid membrane formation in adaxial mesophyll cells was blocked in the Oschr4 mutant. Subcellular localization revealed that OsCHR4::GFP fusion protein was targeted to the nuclei. OsCHR4 was mainly expressed in the root meristem, flower, vascular bundle, and mesophyll cells by promoter::GUS analysis in transgenic rice. The transcripts of some nuclear- and plastid-encoded genes required for early chloroplast development and photosynthesis were decreased in the adaxial albino mesophyll of the Oschr4 mutant. These observations provide evidence that OsCHR4, the rice Mi-2-like protein, plays an important role in early chloroplast development in adaxial mesophyll cells. The results increase our understanding of the molecular mechanism underlying tissue-specific chloroplast development in plants.
[Show abstract][Hide abstract] ABSTRACT: • Auxin has an important role in maintaining optimal root system architecture (RSA) that can cope with growth reductions of crops caused by water or nutrient shortages. However, the mechanism of controlling RSA remains largely unclear. Here, we found a limiting factor of RSA--OsARF12--an auxin response factor whose knockout led to decreased primary root length in rice (Oryza sativa). • OsARF12 as a transcription activator can facilitate the expression of the auxin response element DR5::GFP, and OsARF12 was inhibited by osa-miRNA167d by transient expression in tobacco and rice callus. • The root elongation zones of osarf12 and osarf12/25, which had lower auxin concentrations, were distinctly shorter than for the wild-type, possibly as a result of decreased expression of auxin synthesis genes OsYUCCAs and auxin efflux carriers OsPINs and OsPGPs. The knockout of OsARF12 also altered the abundance of mitochondrial iron-regulated (OsMIR), iron (Fe)-regulated transporter1 (OsIRT1) and short postembryonic root1 (OsSPR1) in roots of rice, and resulted in lower Fe content. • The data provide evidence for the biological function of OsARF12, which is implicated in regulating root elongation. Our investigation contributes a novel insight for uncovering regulation of RSA and the relationship between auxin response and Fe acquisition.
[Show abstract][Hide abstract] ABSTRACT: Auxin transport at least correlates to the three gene families: efflux carriers PIN-formed (PIN), p-glycoprotein (PGP), and influx carrier auxin resistant 1/like aux1(AUX/LAX) in Arabidopsis thaliana. In monocotyledon Sorghum bicolor, the biological function of these genes retains unclear. Our previous study reported that the member analysis, organ-specific expression and expression profiles of the auxin transporter PIN, PGP and AUX/LAX gene families in Sorghum bicolor under IAA, brassinosteroid, polar auxin transport inhibitors and abiotic stresses. Here we further supply the prediction of subcellular localization of SbPIN, SbLAX and SbPGP proteins and discuss the potential relationship between the subcellular localization and stress response. The predicted results showed that the most of SbPIN, SbLAX and SbPGP proteins are localized to the plasma membrane, except few localized to vacuolar membrane and endoplasmic reticulum. This data set provides novel information for investigation of auxin transporters in Sorghum bicolor.
[Show abstract][Hide abstract] ABSTRACT: Auxin is transported by the influx carriers auxin resistant 1/like aux1 (AUX/LAX), and the efflux carriers pin-formed (PIN) and P-glycoprotein (PGP), which play a major role in polar auxin transport. Several auxin transporter genes have been characterized in dicotyledonous Arabidopsis, but most are unknown in monocotyledons, especially in sorghum. Here, we analyze the chromosome distribution, gene duplication and intron/exon of SbPIN, SbLAX and SbPGP gene families, and examine their phylogenic relationships in Arabidopsis, rice and sorghum. Real-time PCR analysis demonstrated that most of these genes were differently expressed in the organs of sorghum. SbPIN3 and SbPIN9 were highly expressed in flowers, SbLAX2 and SbPGP17 were mainly expressed in stems, and SbPGP7 was strongly expressed in roots. This suggests that individual genes might participate in specific organ development. The expression profiles of these gene families were analyzed after treatment with: (a) the phytohormones indole-3-acetic acid and brassinosteroid; (b) the polar auxin transport inhibitors 1-naphthoxyacetic acids, 1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid; and (c) abscissic acid and the abiotic stresses of high salinity and drought. Most of the auxin transporter genes were strongly induced by indole-3-acetic acid and brassinosteroid, providing new evidence for the synergism of these phytohormones. Interestingly, most genes showed similar trends in expression under polar auxin transport inhibitors and each also responded to abscissic acid, salt and drought. This study provides new insights into the auxin transporters of sorghum.
[Show abstract][Hide abstract] ABSTRACT: Sorghum, a C4 model plant, has been studied to develop an understanding of the molecular mechanism of resistance to stress. The auxin-response genes, auxin/indole-3-acetic acid (Aux/IAA), auxin-response factor (ARF), Gretchen Hagen3 (GH3), small auxin-up RNAs, and lateral organ boundaries (LBD), are involved in growth/development and stress/defense responses in Arabidopsis and rice, but they have not been studied in sorghum. In the present paper, the chromosome distribution, gene duplication, promoters, intron/exon, and phylogenic relationships of Aux/IAA, ARF, GH3, and LBD genes in sorghum are presented. Furthermore, real-time PCR analysis demonstrated these genes are differently expressed in leaf/root of sorghum and indicated the expression profile of these gene families under IAA, brassinosteroid (BR), salt, and drought treatments. The SbGH3 and SbLBD genes, expressed in low level under natural condition, were highly induced by salt and drought stress consistent with their products being involved in both abiotic stresses. Three genes, SbIAA1, SbGH3-13, and SbLBD32, were highly induced under all the four treatments, IAA, BR, salt, and drought. The analysis provided new evidence for role of auxin in stress response, implied there are cross talk between auxin, BR and abiotic stress signaling pathways.
No preview · Article · May 2010 · Functional & Integrative Genomics
[Show abstract][Hide abstract] ABSTRACT: The involvement of cytokinins (CTKs) in the repression of phosphate (Pi)-starvation signalling has been widely documented. However, the full physiological and molecular relevance of this role remains unclear. To gain further insights into the regulation system of CTK repression of Pi-starvation signalling, a global analysis of gene expression events in rice seedlings under Pi starvation, and the exogenous CTK treatment under Pi-sufficient (+P) and Pi-deficient (-P) conditions, was conducted using oligonucleotide array analysis. Physiological and biochemical adaptation was observed after 10 d Pi starvation in rice seedlings. A global reduction of the Pi-starvation signalling was detected after 3 d treatment of exogenous CTK. Expression profiling data indicate that, together with a significant increase of intracellular Pi content, many expression changes responsive to Pi starvation were reversed by exogenous CTK treatment while CTK-responsive genes behaved normally under -P condition. These results suggest that the interplay of CTK signal and Pi-starvation response can be partially explained by the rise of Pi concentration after exogenous CTK treatment. Microarray data also revealed that a small number of genes have different CTK response patterns under different Pi levels, suggesting a subtle interaction between CTK and Pi-starvation signalling pathway.
Full-text · Article · Nov 2006 · Plant Cell and Environment