The <i>unc-53</i> gene negatively regulates <i>rac</i> GTPases to inhibit <i>unc-5</i> activity during Distal tip cell migrations in <i>C. elegans</i>

<p>The <i>unc-53</i>/NAV2 gene encodes for an adaptor protein required for cell migrations along the anteroposterior (AP) axes of <i>C. elegans</i>. This study identifies <i>unc-53</i> as a novel component of signaling pathways regulating Distal tip cell (DTC) migrations along the AP and dorsoventral (DV) axes. <i>unc-53</i> negatively regulates and functions downstream of <i>ced-10</i>/Rac pathway genes; <i>ced-10</i>/Rac and <i>mig-</i>2/RhoG, which are required for proper DTC migration. Moreover, <i>unc-53</i> exhibits genetic interaction with <i>abl-1</i> and <i>unc-5</i>, the 2 known negative regulators of <i>ced-10</i>/Rac signaling. Our genetic analysis supports the model, where <i>abl-1</i> negatively regulates <i>unc-53</i> during DTC migrations and requirement of <i>unc-53</i> function during both AP and DV DTC migrations could be due to <i>unc-53</i> mediated regulation of <i>unc-5</i> activity.</p

Structural features of rice phospholipase C family.

<p>(A) Exon-intron organization is shown for both PI-PLC and NPC groups of rice PLCs and the gene names are mentioned at left. Genes are shown according to their phylogenetic clustering and not in the order of their numbers. Purple bars represent the exon, lines represent the intron while grey colour bars indicate the un-translated region (UTR) both at 5′ and 3′ position. (B) Protein structure of rice PLC gene family is showing the presence of highly conserved characteristic domains PI-PLC-X (Pfam identity- PF00388), PI-PLC-Y (PF00387) and C2 (PF00168) in all the PI-PLC members while EF hand like motif (PF09279) was marked only in two of the members. Phosphoesterase (PF04185) domain is present in all the NPC members. Numbers on each domain depict amino acid residue at the start and end of a particular domain and direction of a protein is depicted by N and C terminal.</p

Promoter analysis of rice PLC gene family.

<p><i>Cis</i>-regulatory elements in the 1 kb upstream region (from translation start site) of the promoter of all the rice PLC genes were analysed using PlantCARE database. Various elements such as ABRE, MBS, TC-rich repeat, C-repeat/DRE, RY-elements, Skn-1 and GCN4 are present in the forward and reverse strands and are indicated by the arrowhead mark above and below the line, respectively. Scale over the promoters indicates the specific location of the elements. Differential regulation (up- or down-regulation) of the genes under different abiotic stresses; S-salt, C-cold, D-drought and during reproductive developmental phases; P- panicle and Sd- seed, is indicated on the right side of each gene.</p

Subcellular localization of OsPLC proteins in <b><i>Nicotiana benthamiana</i></b><b> cells.</b>

<p>Agrobacterium-infiltrated tobacco leaves expressing the GFP-PLC fusion protein driven by the 2XCaMV 35S promoter. Confocal images of fluorescence (green) for cell expressing OsPLC1 and OsPLC4 are showing their distribution throughout the cytoplasm and nucleus (first and second row). Expressed GFP-OsNPC1 fusion protein, mainly localized to cytoplasm and small spots like structures in the cell (third row), and GFP-OsNPC3 fusion protein showed preferential localization to small punctate structures in the cell (fourth row). Cells transformed with vector only (CaMV35S-GFP) are shown in the lowermost row. All the images were taken in 5 different sections in z direction and merges together. Scale bar = 40 µm.</p

Various features of PLC genes in rice genome.

<p>Various features of PLC genes in rice genome.</p

Co-localization of rice NPC proteins with chlorophyll auto-fluorescence of the cell.

<p>Confocal images of <i>Nicotiana benthamiana</i> cell expressing GFP-OsNPC1 (upper panel) and GFP-OsNPC3 (lower panel). Green GFP signal merges with red auto-fluorescence of chloroplast, as seen in the merged regions (yellowish orange) in the overlay. All the images were taken in 5 different sections in z direction and merges together. Scale bar = 40 µm.</p

Microarray expression profile validation by quantitative RT-PCR for rice PLC gene family under abiotic stresses.

<p>Microarray expression profile was generated using three biological replicate and two biological replicates were used for Q-PCR expression analysis. Standard error bars have been shown for the data from both the techniques. Y-axis represents the normalized expression values and X-axis represents different experimental conditions. Green and grey columns denote the expression values from microarray and real time PCR, respectively.</p

Expression profile of rice PLC gene family during developmental stages.

<p>Average signal intensity (GCRMA) value of three replicates from microarray for all the developmental stages (three vegetative; L-mature leaf, R-root, SDL-seven day old seedling, six panicle stages; P1–P6 and five seed stages; S1–S5) has been plotted to show the differential expression. Standard error bars have been shown. Y-axis represents signal values from microarray and X-axis shows different developmental stages.</p

Phylogenetic relationship of rice and <b><i>Arabidopsis</i></b><b> PLC gene family.</b>

<p>An un-rooted neighbour joining phylogenetic tree was constructed from the protein sequences of rice and <i>Arabidopsis</i> PLCs, including both PI-PLCs and NPCs. Multiple sequence alignment was carried out using clustalX2.0 and the tree was generated using MEGA5. Rice and <i>Arabidopsis</i> PI-PLCs and NPCs are clustered together based on significant bootstrap value (>50%). Scale bar indicates 0.1 amino acid substitution per site.</p

Gene Expression Analysis of Rice Seedling under Potassium Deprivation Reveals Major Changes in Metabolism and Signaling Components

<div><p>Plant nutrition is one of the important areas for improving the yield and quality in crops as well as non-crop plants. Potassium is an essential plant nutrient and is required in abundance for their proper growth and development. Potassium deficiency directly affects the plant growth and hence crop yield and production. Recently, potassium-dependent transcriptomic analysis has been performed in the model plant <i>Arabidopsis</i>, however in cereals and crop plants; such a transcriptome analysis has not been undertaken till date. In rice, the molecular mechanism for the regulation of potassium starvation responses has not been investigated in detail. Here, we present a combined physiological and whole genome transcriptomic study of rice seedlings exposed to a brief period of potassium deficiency then replenished with potassium. Our results reveal that the expressions of a diverse set of genes annotated with many distinct functions were altered under potassium deprivation. Our findings highlight altered expression patterns of potassium-responsive genes majorly involved in metabolic processes, stress responses, signaling pathways, transcriptional regulation, and transport of multiple molecules including K⁺. Interestingly, several genes responsive to low-potassium conditions show a reversal in expression upon resupply of potassium. The results of this study indicate that potassium deprivation leads to activation of multiple genes and gene networks, which may be acting in concert to sense the external potassium and mediate uptake, distribution and ultimately adaptation to low potassium conditions. The interplay of both upregulated and downregulated genes globally in response to potassium deprivation determines how plants cope with the stress of nutrient deficiency at different physiological as well as developmental stages of plants.</p></div