Ravishankar Palanivelu

The University of Arizona | UA · School of Plant Sciences

Synergid cells in the micropylar end of the female gametophyte are required for critical cell–cell signaling interactions between the pollen tube and the ovule that precede double fertilization and seed formation in flowering plants. LORELEI (LRE) encodes a putative GPI-anchored protein that is expressed primarily in the synergid cells, and togethe...

Synergid cells in the micropylar end of the female gametophyte are required for critical cell-cell signaling interactions between the pollen tube and the ovule that precede double fertilization and seed formation in flowering plants. LORELEI ( LRE ) encodes a GPI-anchored protein that is expressed primarily in the synergid cells, and together with...

The coordinated development of sporophytic and gametophytic tissues is essential for proper ovule patterning and fertility. However, the mechanisms regulating their integrated development remain poorly understood. Here, we report that the Swi2/Snf2-Related1 (SWR1) chromatin remodeling complex acts with the ERECTA receptor kinase signaling pathway t...

Key message: Glycosylphosphatidylinositol (GPI)-anchored proteins (GAPs) are a unique type of membrane-associated proteins in eukaryotes. GPI and GAP biogenesis and function have been well studied in non-plant models and play an important role in the fertility of mouse sperm and egg. Although GPI and GAP biogenesis and function in plants are less...

Background: Glycosylphosphatidylinositol (GPI) addition is one of the several post-translational modifications to proteins that increase their affinity for membranes. In eukaryotes, the GPI transamidase complex (GPI-T) catalyzes the attachment of pre-assembled GPI anchors to GPI-anchored proteins (GAPs) through a transamidation reaction. A mutatio...

Reverse genetics approaches for characterizing phenotypes of mutants in a gene of interest (GOI) require thorough genotyping and phenotypic analysis. However, special challenges are encountered when a GOI is expressed in reproductive tissues: a variety of assays are required to characterize the phenotype and a mutant may show sporophytic and/or gam...

Background Glycosylphosphatidylinositol (GPI) addition is one of the several post-translational modifications to proteins that increase their affinity for membranes. In eukaryotes, the GPI transamidase complex (GPI-T) catalyzes the attachment of pre-assembled GPI anchors to GPI-anchored proteins (GAPs) through a transamidation reaction. A mutation...

A signaling complex comprising members of the LORELEI (LRE)-LIKE GPI-anchored protein (LLG) and Catharanthus roseus RECEPTOR-LIKE KINASE 1-LIKE ( Cr RLK1L) families perceive RAPID ALKALINIZATION FACTOR (RALF) peptides and regulate growth, reproduction, immunity, and stress responses in Arabidopsis. Genes encoding these proteins are members of multi...

In flowering plants, pollen tubes undergo tip growth to deliver two nonmotile sperm to the ovule where they fuse with an egg and central cell to achieve double fertilization. This extended journey involves rapid growth and changes in gene activity that manage compatible interactions with at least seven different cell types. Nearly half of the genom...

In flowering plants, cell-cell communication plays a key role in reproductive success, as both pollination and fertilization require pathways that regulate interactions between many different cell types. Some of the most critical of these interactions are those between the pollen tube (PT) and the embryo sac, which ensure the delivery of the sperm...

Germ-line specification is essential for sexual reproduction. In the ovules of most flowering plants, only a single hypodermal cell enlarges and differentiates into a megaspore mother cell (MMC), the founder cell of the female germ-line lineage. The molecular mechanisms restricting MMC specification to a single cell remain elusive. We show that the...

In flowering plants the female gametophyte controls pollen tube reception immediately before fertilization and regulates seed development immediately after fertilization, although controlling mechanisms remain poorly understood. Previously, we showed that LORELEI (LRE), which encodes a putative glycosylphosphatidylinositol (GPI)-anchored membrane p...

The world is now facing many severe problems due to increasing global demands for alreadylimiting food and energy resources. Plant reproduction is crucial not only for producing offspringbut also for improving crop quality and yield. Moreover, plant reproduction entails complex growthand developmental processes, which offer various opportunities fo...

We propose a robust method for estimating dynamic 3D curvilinear branching structure from monocular images. While 3D reconstruction from images has been widely studied, estimating thin structure has received less attention. This problem becomes more challenging in the presence of camera error, scene motion, and a constraint that curves are attached...

We propose a robust method for estimating dynamic 3D curvilinear branching structure from monocular images. While 3D reconstruction from images has been widely studied, estimating thin structure has received less attention. This problem becomes more challenging in the presence of camera error, scene motion, and a constraint that curves are attached...

[This corrects the article DOI: 10.1371/journal.pgen.1000621.].

RT-PCR analysis of gene expression. Total RNA from indicated tissues—dry pollen, 0.5 h PT, 4 h PT, 8- and 21-day-old seedlings (DS)—was used as templates to perform oligo-dT primed reverse transcription reactions followed by cDNA synthesis. RT-PCR was performed with cDNAs from indicated tissues and gel images of PCR products amplified are shown. (A...

In angiosperms, pollen tube reception by the female gametophyte is required for sperm release and double fertilization. In Arabidopsis thaliana lorelei (lre) mutants, pollen tube reception fails in most female gametophytes, which thus remain unfertilized. LORELEI (LRE) encodes a putative glycophosphatidylinositol (GPI)-anchored surface protein with...

In angiosperms, pollen tube reception by the female gametophyte is required for sperm release and double fertilization. In Arabidopsis thaliana lorelei (lre) mutants, pollen tube reception fails in most female gametophytes, which thus remain unfertilized. LORELEI (LRE) encodes a putative glycophosphatidylinositol (GPI)-anchored surface protein with...

IIn flowering plant reproduction pollen tube reception is the signaling system that results in pollen tube discharge, synergid degeneration, and successful delivery of male gametes (two sperm cells) to the site where they can fuse with female gametes (egg cell and central cell). Some molecules required for this complex and essential signaling excha...

In flowering plants, meiocytes develop from subepidermal cells in anthers and ovules. The mechanisms that integrate gene-regulatory processes with meiotic programs during reproductive development remain poorly characterized. Here, we show that Arabidopsis thaliana plants deficient in ACTIN-RELATED PROTEIN6 (ARP6), a subunit of the SWR1 ATP-dependen...

γ-Aminobutyric acid (GABA) is implicated in pollen tube growth, but the molecular and cellular mechanisms that it mediates are largely unknown. Here, it is shown that exogenous GABA modulates putative Ca2+-permeable channels on the plasma membranes of tobacco pollen grains and pollen tubes. Whole-cell voltage-clamp experiments and non-invasive micr...

In flowering plants, meiocytes develop from subepidermal cells in anthers and ovules. The mechanisms that integrate gene-regulatory processes with meiotic programs during reproductive development remain poorly characterized. Here, we show that Arabidopsis thaliana plants deficient in ACTIN-RELATED PROTEIN6 (ARP6), a subunit of the SWR1 ATP-dependen...

In flowering plants, immotile sperm cells develop within the pollen grain and are delivered to female gametes by a pollen tube [1, 2]. Upon arrival at the female gametophyte, the pollen tube stops growing and releases sperm cells for successful fertilization [3]. Several female signaling components essential for pollen tube reception have been iden...

This disclosure relates, inter alia, to stimulants of pollen tube germination and growth of pollen tubes, and methods of their use to stimulate in vitro and in vivo pollen germination and pollen tube growth.

Two related B3 domain transcriptional repressors, HSI2 (HIGH-LEVEL EXPRESSION OF SUGAR-INDUCIBLE GENE2)/VAL1 (VP1/ABI3-LIKE1) and HSL1 (HSI2-LIKE1)/VAL2, function redundantly to repress key transcriptional regulators of seed maturation genes in Arabidopsis thaliana seedlings. Using a forward genetic screen designed to isolate trans-acting mutants t...

Sexual reproduction in flowering plants is unique in multiple ways. Distinct multicellular gametophytes contain either a pair of immotile, haploid male gametes (sperm cells) or a pair of female gametes (haploid egg cell and homodiploid central cell). After pollination, the pollen tube, a cellular extension of the male gametophyte, transports both m...

Polarized cell elongation is triggered by small molecule cues during development of diverse organisms. During plant reproduction, pollen interactions with the stigma result in the polar outgrowth of a pollen tube, which delivers sperm cells to the female gametophyte to effect double fertilization. In many plants, pistils stimulate pollen germinatio...

We present a general model for tracking smooth trajectories of multiple targets in complex data sets, where tracks potentially cross each other many times. As the number of overlapping trajectories grows, exploiting smoothness becomes increasingly important to disambiguate the association of successive points. However, in many important problems an...

We present a novel microsystem-based assay to assess and quantify pollen tube behavior in response to pistil tissues. During plant reproduction, signals from female tissues (pistils) guide the sperm-carrying pollen tube to the egg cell to achieve fertilization and initiate seed development. Existing pollen tube guidance bioassays are performed in a...

GABA (γ-aminobutyric acid), a non-protein amino acid, is a signaling factor in many organisms. In plants, GABA is known to accumulate under a variety of stresses. However, the consequence of GABA accumulation, especially in vegetative tissues, remains poorly understood. Moreover, gene expression changes as a consequence of GABA accumulation in plan...

Background: Pollen tubes deliver sperm after navigating through flower tissues in response to attractive and repulsive cues. Genetic analyses in maize and Arabidopsis thaliana and cell ablation studies in Torenia fournieri have shown that the female gametophyte (the 7-celled haploid embryo sac within an ovule) and surrounding diploid tissues are es...

ISS poster - published in 2012

Double fertilization, uniquely observed in plants, requires successful sperm cell delivery by the pollen tube to the female gametophyte, followed by migration, recognition and fusion of the two sperm cells with two female gametic cells. The female gametophyte not only regulates these steps but also controls the subsequent initiation of seed develop...

The pollen tube represents an attractive model system for functional genomic analysis of the cell-cell interactions that mediate guided cellular growth. The pollen tube extends through pistil tissues and responds to guidance cues that direct the tube towards an ovule, where it releases sperm for fertilization. Pollen is readily isolated from anther...

In plants, double fertilization requires successful sperm cell delivery into the female gametophyte followed by migration, recognition and fusion of the two sperm cells with two female gametes. We isolated a null allele (lre-5) of LORELEI, which encodes a putative glycosylphosphatidylinositol (GPI)-anchored protein implicated in reception of the po...

Pollen tubes extend through pistil tissues and are guided to ovules where they release sperm for fertilization. Although pollen tubes can germinate and elongate in a synthetic medium, their trajectory is random and their growth rates are slower compared to growth in pistil tissues. Furthermore, interaction with the pistil renders pollen tubes compe...

Raw gene expression data for dry pollen (6.27 MB XLS)

Raw gene expression data for 0.5 h PT (6.27 MB XLS)

Raw gene expression data for 4 h PT (6.27 MB XLS)

Raw gene expression data for SIV PT. Normalized expression data (log2) for each replicate of dry pollen, 0.5 h PT, 4 h PT, SIV PT, and 25 selected experiments from publicly available sources; and statistical analyses for selected comparisons. (5.95 MB XLS)

Complete list of overrepresented GO terms shown in Figure 2C and Figure 2E (2.25 MB XLS)

Statistical analysis of gene expression changes between SIV PT and dry pollen (1.36 MB XLS)

Genes that best discriminate the SIV PT cluster from other pollen clusters (0.06 MB DOC)

Five insertions cause defects in pollen tube growth in vitro. Pollen heterozygous for the indicated insertion was grown in vitro for 6 hours and then stained for GUS expression. GUS+ (blue) pollen tubes carry insertions; GUS- (white) pollen tubes are wild type. In control pollen (A), the GUS+ (blue) pollen tubes are as long and as numerous as GUS-...

Members of subgroup 18 are expressed in growing pollen tubes. Mean microarray expression data (log2, Table S5) are plotted for each of the cell or tissue types analyzed in this study for seven genes that comprise MYB subgroup 18 [60],[61]. (0.25 MB TIF)

Normalized expression data (log2) for each replicate of dry pollen, 0.5 h PT, 4 h PT, SIV PT, and 25 selected experiments from publicly available sources; and statistical analyses for selected comparisons. Statistical analyses of significant differences between two indicated conditions are described in Materials and Methods. The table has been sort...

SIV PT-enriched genes (0.51 MB XLS)

Statistical analysis of significant gene expression changes between 0.5 h PT and dry pollen (0.05 MB XLS)

Statistical analysis of gene expression changes between 4 h PT and 0.5 h PT (0.15 MB XLS)

Statistical analysis of gene expression changes between 4 h PT and dry pollen (0.21 MB XLS)

Syngenta Arabidopsis Insertion Lines (SAIL) analyzed (0.04 MB XLS)

List of primers used in RT-PCR and qRT-PCR experiments (0.02 MB XLS)

Heat maps representing microarray data. (A) Genes analyzed by qRT-PCR (Figure 3, Figure 4, and Table 3). Relative expression values obtained from microarray analysis (Table S5) are shown as a heat map. For each gene, the highest value is set at 100% and the relative value is calculated for other samples. (B) Genes chosen for reverse genetic analysi...

Pearson correlation coefficients between microarray experiments. The Pearson correlation coefficients between quantile normalized 40 microarray data sets used in this study are shown. (0.04 MB XLS)

Complete list of overrepresented GO terms and the associated genes from the Fisher exact test shown in Table 1 (0.17 MB XLS)

Statistical analysis of gene expression changes between SIV PT v 4 h PT (0.99 MB XLS)

Hierarchical clustering of pollen arrays. Agglomerative hierarchical clustering of the fifteen microarrays representing four pollen conditions was performed to generate the dendrogram. (0.09 MB TIF)