Current Status of Conventional and Molecular Interventions for Blast Resistance in Rice

Pyricularia oryzae anamorph of Magnaporthe oryzae is one of the most notorious fungal pathogens causing severe economic loss in rice production worldwide. Various methods, viz. cultural, biological and molecular approaches, are utilized to counteract this pathogen. Moreover, some tolerant or resistant rice varieties have been developed with the help of breeding programmes. Isolation and molecular characterization of different blast resistance genes now open the gate for new possibilities to elucidate the actual allelic variants of these genes via various molecular breeding and transgenic approaches. However, the behavioral pattern of this fungus breakups the resistance barriers in the resistant or tolerant rice varieties. This host-pathogen barrier will be possibly countered in future research by comparative genomics data from available genome sequence data of rice and M. oryzae for durable resistance. Present review emphasized fascinating recent updates, new molecular breeding approaches, transgenic and genomics approaches(i.e. mi RNA and genome editing) for the management of blast disease in rice. The updated information will be helpful for the durable, resistance breeding programme in rice against blast pathogen.

Genotypic Variation in Spatial Distribution of Fe in Rice Grains in Relation to Phytic Acid Content and Ferritin Gene Expression

Rice varieties having high Fe concentration in the endospermic region can be used as a good source for Fe deficit population.In this study,303 Oryza sativa varieties and 1 Oryza rufipogon accession were assessed for spatial Fe accumulation in grains by Prussian blue staining method.Spatial ferritin protein distribution in grains was visualized by immunohistochemistry,and ferritin expression was assessed in selected rice varieties using semi-quantitative reverse transcription PCR.Three popular rice varieties,namely Sarjoo 52,Madhukar and Jalmagna,and the O.rufipogon variety showed Fe in all the regions of grains,and the highest Fe concentration was observed in the embryo region.Some high-yielding varieties like Swarna,Swarna Sub 1,CSR13 and NDRR359 had lower Fe concentration in the embryo region.The highest Fe concentration was detected in O.rufipogon(49.8μg/g),followed by Sarjoo 52(26.1μg/g)and Madhukar(25.7μg/g).Phytic acid concentration was the minimum in O.rufipogon(5.75 mg/g)followed by Sarjoo 52(5.83 mg/g).Western blot and semi-quantitative reverse transcription PCR showed higher expression of ferritin gene in O.rufipogon,Sarjoo 52 and Madhukar.In conclusion,O.rufipogon and Sarjoo 52 had higher Fe concentration in the embryo regions as well as endosperm and aleurone layer,whereas the other varieties had lower Fe concentration in the endosperm.Sarjoo 52 could be used as a donor in the rice breeding program for the generation of new varieties with elevated grain Fe concentration.

Genome-Wide Comparative in silico Analysis of Calcium Transporters of Rice and Sorghum

The mechanism of calcium uptake, translocation and accumulation in Poaceae has not yet been fully understood. To address this issue, we conducted genome-wide comparative in silico analysis of the calcium （Ca2＋） transporter gene family of two crop species, rice and sorghum. Gene annotation, identification of upstream cis-acting ele- ments, phylogenetic tree construction and syntenic mapping of the gene family were performed using several bio- informatics tools. A total of 31 Ca2＋ transporters, distributed on 9 out of 12 chromosomes, were predicted from rice genome, while 28 Ca2＋ transporters predicted from sorghum are distributed on all the chromosomes except chromosome 10 （Chr 10）. Interestingly, most of the genes on Chr 1 and Chr 3 show an inverse syntenic relation- ship between rice and sorghum. Multiple sequence alignment and motif analysis of these transporter proteins re- vealed high conservation between the two species. Phylogenetic tree could very well identify the subclasses of channels, ATPases and exchangers among the gene family. The in silico c/s-regulatory element analysis suggested diverse functions associated with light, stress and hormone responsiveness as well as endosperm- and meris- tem-specific gene expression. Further experiments are warranted to validate the in silico analysis of the predicted transporter gene family and elucidate the functions of Ca2＋ transporters in various biological processes.

In silico Analysis of Sequential,Structural and Functional Diversity of Wheat Cystatins and Its Implication in Plant Defense

Phytocystatins constitute a multigene family that regulates the activity of endogenous and/or exogenous cysteine proteinases. Cereal crops like wheat are continuously threatened by a multitude of pathogens, therefore cystatins offer to play a pivotal role in deciding the plant response. In order to study the need of having diverse specificities and activities of various cystatins, we conducted comparative analysis of six wheat cystatins （WCs） with twelve rice, seven barley, one sorghum and ten corn cystatin sequences employing different bioinformatics tools. The obtained results identified highly conserved signature sequences in all the cystatins considered. Several other motifs were also identified, based on which the sequences could be categorized into groups in congruence with the phylogenetic clustering. Homology modeling of WCs revealed 3D structural topology so well shared by other cystatins. Protein-protein interaction of WCs with papain supported the notion that functional diversity is a con- sequence of existing differences in amino acid residues in highly conserved as well as relatively less conserved motifs. Thus there is a significant conservation at the sequential and structural levels; however, concomitant variations maintain the functional diversity in this protein family, which constantly modulates itself to reciprocate the diversity while counteracting the cysteine proteinases.