Genetic Dissection of Grain Size Traits Through Genome-Wide Association Study Based on Genic Markers in Rice

Not AvailableGrain size plays a significant role in rice, starting from affecting yield to consumer preference, which is the driving force for deep investigation and improvement of grain size characters. Quantitative inheritance makes these traits complex to breed on account of several alleles contributing to the complete trait expression. We employed genome-wide association study in an association panel of 88 rice genotypes using 142 new candidate gene based SSR (cgSSR) markers, derived from yield-related candidate genes, with the efficient mixed-model association coupled mixed linear model for dissecting complete genetic control of grain size traits. A total of 10 significant associations were identified for four grain size-related characters (grain weight, grain length, grain width, and length-width ratio). Among the identified associations, seven marker trait associations explain more than 10% of the phenotypic variation, indicating major putative QTLs for respective traits. The allelic variations at genes OsBC1L4, SHO1 and OsD2 showed association between 1000-grain weight and grain width, 1000-grain weight and grain length, and grain width and length-width ratio, respectively. The cgSSR markers, associated with corresponding traits, can be utilized for direct allelic selection, while other significantly associated cgSSRs may be utilized for allelic accumulation in the breeding programs or grain size improvement. The new cgSSR markers associated with grain size related characters have a significant impact on practical plant breeding to increase the number of causative alleles for these traits through marker aided rice breeding programs.Not Availabl

Development of Broad Spectrum and Durable Bacterial Blight Resistant Variety through Pyramiding of Four Resistance Genes in Rice

Not AvailableBacterial blight (BB) disease caused by Xanthomonas oryzae pv. oryzae is a major biotic constraint on obtaining higher grain yields in rice. Marker-assisted backcross breeding (MABB) was performed by the pyramiding of Xa4, xa5, xa13 and Xa21 resistance genes in the popular variety, Ranidhan. A foreground selection in BC1F1, BC2F1, and BC3F1 progenies detected all the target genes in 12, 7 and 16 progenies by using the closely linked markers from a population size of 426, 410, and 530, respectively. The BB-positive progenies carrying the target genes with a maximal similarity to the recipient parent was backcrossed in each backcross generation. A total of 1784 BC3F2 seeds were obtained from the best BC3F1 progeny. The screening of the BC3F2 progenies for the four target genes resulted in eight plants carrying all the four target genes. A bioassay of the pyramided lines conferred very high levels of resistance to the predominant isolates of bacterial blight disease. In addition, these pyramided lines were similar to Ranidhan in 16 morpho-quality traits, namely, plant height, filled grains/panicle, panicles/plant, grain length, grain breadth, grain weight, milling, head rice recovery, kernel length after cooking, water uptake, the volume expansion ratio, gel consistency,alkali-spreading value, and the amylose content.Not Availabl

Not Available

Not AvailableLow light (LL) stress during the grain-filling stage acutely impairs the quality and quantity of starch accumulation in rice grains. Here, we observed that LL-induced poor starch biosynthesis is modulated by auxin homeostasis, which regulates the activities of major carbohydrate metabolism enzymes such as starch synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) in rice. Further, during the grain-filling period under LL, the starch/sucrose ratio increased in leaves but significantly decreased in the developing spikelets. This suggests poor sucrose biosynthesis in leaves and starch in the grains of the rice under LL. A lower grain starch was found to be correlated with the depleted AGPase and SS activities in the developing rice grains under LL. Further, under LL, the endogenous auxin (IAA) level in the spikelets was found to be synchronized with the expression of a heteromeric G protein gene, RGB1. Interestingly, under LL, the expression of OsYUC11 was significantly downregulated, which subsequently resulted in reduced IAA in the developing rice spikelets, followed by poor activation of grain-filling enzymes. This resulted in lowered grain starch accumulation, grain weight, panicle number, spikelet fertility, and eventually grain yield, which was notably higher in the LL-susceptible (GR4, IR8) than in the LL-tolerant (Purnendu, Swarnaprabha) rice genotypes. Therefore, we hypothesize that depletion in auxin biosynthesis under LL stress is associated with the downregulation of RBG1, which discourages the expression and activities of grain-filling enzymes, resulting in lower starch production, panicle formation, and grain yield in rice.Not Availabl

Not Available

Not AvailableRecent outbreak of Coronavirus disease (COVID-19) pandemic around the world is associated with ‘severe acute respiratory syndrome’ (SARS-CoV2) in humans. SARS-CoV2 is an enveloped virus and E proteins present in them are reported to form ion channels, which is mainly associated with pathogenesis. Thus, there is always a quest to inhibit these ion channels, which in turn may help in controlling diseases caused by SARS-CoV2 in humans. Considering this, in the present study, authors employed computational approaches for studying the structure as well as function of the human ‘SARS-CoV2 E’ protein as well as its interaction with various phytochemicals. Result obtained revealed that a-helix and loops present in this protein experience random movement under optimal condition, which in turn modulate ion channel activity; thereby aiding the pathogenesis caused via SARS-CoV2 in human and other vertebrates. However, after binding with Belachinal, Macaflavanone E, and Vibsanol B, the random motion of the human ‘SARS-CoV2 E’ protein gets reduced, this, in turn, inhibits the function of the ‘SARS-CoV2 E’ protein. It is pertinent to note that two amino acids, namely VAL25 and PHE26, play a key role while interacting with these three phytochemicals. As these three phytochemicals, namely, Belachinal, Macaflavanone E & Vibsanol B, have passed the ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) property as well as ‘Lipinski’s Rule of 5s’, they may be utilized as drugs in controlling disease caused via SARS-COV2, after further investigation.Not Availabl

The impact of natural selection on gene associated with panicle number formation in Oryza sativa

Panicle number is directly associated with grain number in rice. As the panicle number increases, it affects the total yield of rice. We examined the evolution of genes associated with panicle number formation in Oryza sativa. Intramural program written in JAVA script and fastPHASE software used for the generation of genotype and haplotype file of SNPs of 11 individual genes associated with panicle number formation utilizing VCF file obtained from RiceCAP project (USDA/CSREES http://www.uark.edu/ua/ricecap/).Tests for natural selection executed on these genes using the Haplotype data. Tajima’s D and Fu Li’s D* analysis were performed using DNASP v4.0. Rates of non-synonymous Vs synonymous changes were calculated according to the dN/dS algorithm of Nei and Gojobori.dN/dS calculation compared with the ancestral (Oryza meridionalis) sequence individually showed that out of 11, almost all genes responsible for grain number formation, Os01g0746400, Os03g0203200, Os03g0706500, Os04g0550600, Os06g0127800, Os06g0154200, Os06g0610350, Os06g0660200, Os08g0162100 and Os11g0528700 are negatively selected throughout evolution., Although Tajima’s D was not found significant, the negative value for 8 genes, Os01g0746400, Os03g0123300, Os03g0706500, Os06g0127800, Os06g0610350, Os06g0660200, Os08g0162100 and Os11g0528700 indicated that  low frequency variants are more in number than high frequency variants. For Fu Li’s D*, the significantly negative values in most of the genes, Os01g0746400, Os03g0123300, Os03g0706500, Os06g0127800, Os06g0610350, Os08g0162100 and Os11g0528700, indicated that the high frequency variants detected through Tajima’s D are predominantly singletons. Thus, result from dN/dS, Tajima’s D and Fu Li indicated that negative (purifying) selection acts on genes responsible for panicle number formation.These results will be useful for further investigation on  how the genes associated with panicle number and how purifying selection result in stabilizing selection through the purging of deleterious variations that arise

In silico identification and characterization of differential expressed genes (DEGs) associated with grain and panicle number in rice

Grain number is an important trait for yield in rice. Several genes have been identified controlling grain and panicle number, which has direct or indirect effect on yield. Some genes play a key role for panicle formation and number of panicles per plant. The number of panicles per plant is directly regulating the grain number per plant. In present study, in silico approach was adopted for identifying differentially expressed genes associated with grain number and panicle number. Further, pathway enrichment analysis of these genes performed. The microarray data, GSE51616, downloaded from the GEO database originally submitted by Wang et al. (2014).Young leaves in vegetative stage (35-days old) and developing panicles (0.1cm) from field-grown OX-Ghd7HJ19 transgenic and wild-type plants with two biological replicates were used to isolate RNA for chip analysis. Background correction and normalization of raw microarray data was carried out using the Robust Multichip Averaging (RMA) method of affy packages of R (v. 3.1.3). The linear regression model package, limma was utilized to classify chips into two groups. The Bayes method (Benjamini and Hochberg) was used to correct for multiple testing. Adjusted P-value < 0.01 and |logFC| > 2 was used as a cut-off to identify differentially expressed genes. We identified 393 differentially expressed genes, which mainly belongs to either Phosphatidylethanolamine-binding protein family or DUF3778 domain family. Proteins of these two families regulate formation of high grain number as well as panicle number. These genes like Ghd7, Ehd1, Dep1, Os10g0463400, Os03g0752800, Os03g0215400, Os06g0157700 and Os06g0157500 function to integrate the dynamic environmental inputs with phase transition, architecture regulation, and stress response to maximize the reproductive success of the rice plant. Thus, these genes can act as potential target protein for increasing grain and panicle number in rice plant, which will lead to increase in yield of rice grain

Identification and expression analysis of miRNAs and elucidation of their role in salt tolerance in rice varieties susceptible and tolerant to salinity.

Soil salinization is a serious problem for cultivation of rice, as among cereals rice is the most salt sensitive crop, and more than 40% of the total agricultural land amounting to approximately 80 million ha the world over is salt affected. Salinity affects a plant in a varieties of ways, including ion toxicity, osmotic stress and oxidative damage. Since miRNAs occupy the top place in biochemical events determining a trait, understanding their role in salt tolerance is highly desirable, which may allow introduction of the trait in the rice cultivars of choice through biotechnological interventions. High throughput sequencing of sRNAs in the root and shoot tissues of the seedlings of the control and NaCl treated Pokkali, a salt-tolerant rice variety, identified 75 conserved miRNAs and mapped 200 sRNAs to the rice genome as novel miRNAs. Expression of nine novel miRNAs and two conserved miRNAs were confirmed by Northern blotting. Several of both conserved and novel miRNAs that expressed differentially in root and/or shoot tissues targeted transcription factors like AP2/EREBP domain protein, ARF, NAC, MYB, NF-YA, HD-Zip III, TCP and SBP reported to be involved in salt tolerance or in abiotic stress tolerance in general. Most of the novel miRNAs expressed in the salt tolerant wild rice Oryza coarctata, suggesting conservation of miRNAs in taxonomically related species. One of the novel miRNAs, osa-miR12477, also targeted L-ascorbate oxidase (LAO), indicating build-up of oxidative stress in the plant upon salt treatment, which was confirmed by DAB staining. Thus, salt tolerance might involve miRNA-mediated regulation of 1) cellular abundance of the hormone signaling components like EREBP and ARF, 2) synthesis of abiotic stress related transcription factors, and 3) antioxidative component like LAO for mitigation of oxidative damage. The study clearly indicated importance of osa-miR12477 regulated expression of LAO in salt tolerance in the plant

Not Available

Not AvailableSeed germination plays cardinal roles in seedling establishment and their successive growth. However, seed germination is retarded by far-red (FR) enrichment under low light stress, and the inhibitory signalling mechanism remains ambiguous. Our results indicated that low light treatment, both in the open and growth chamber conditions, inhibits rice seed germination by decreasing the gibberellin (GA) contents. To explore the mechanism of GA-deficiency under low light stress, differential expression profiling of GA-anabolic, -catabolic, ABA -anabolic, catabolic, and SLR1 was investigated, revealing that expression of ABA- anabolic, GA-catabolic genes and SLR1 was upregulated with a simultaneous downregulation of ABA-catabolic and GA-anabolic genes under low light treatment. These results suggested that FR-induced GA inadequacy is resulted by upregulation of SLR1 and GAcatabolism genes consequently increase DELLA that further subsided GA-responses in the germinating rice seeds. Moreover, we provided evidence that FR-induced GA inadequacy demotes rice seed germination by decreasing amylase activity, eventually decreasing the carbohydrate solubilization in the germinating seeds. Finally, we suggest that under low light stress, due to a retarded conversion of phytochrome A to their bioactive form, the ABA-catabolic genes were eventually upregulated with a simultaneous downregulation of GA-anabolic genes. Consequently, a lower GA pool fails to leverage the GA-dependent DELLA degradation, further shutting down the expected GA responses that reduce germination efficiency under FRenriched light.Not Availabl