RESUMO
The genomes of an elite rice restorer line KMR3 (salinity-sensitive) and its salinity-tolerant introgression line IL50-13, a popular variety of coastal West Bengal, India, were sequenced. High-quality paired-end reads were obtained for KMR3 (147.6 million) and IL50-13 (131.4 million) with a sequencing coverage of 30X-39X. Scaffolds generated from the pre-assembled contigs of each sequenced genome were mapped separately onto the reference genome of Oryza sativa ssp. japonica cultivar Nipponbare to identify genomic variants in terms of SNPs and InDels. The SNPs and InDels identified for KMR3 and IL50-13 were then compared with each other to identify polymorphic SNPs and InDels unique and common to both the genomes. Functional enrichment analysis of the protein-coding genes with unique InDels identified GO terms involved in protein modification, ubiquitination, deubiquitination, peroxidase activity, and antioxidant activity in IL50-13. Linoleic acid metabolism, circadian rhythm, and alpha-linolenic acid metabolism pathways were enriched in IL50-13. These GO terms and pathways are involved in reducing oxidative damage, thus suggesting their role in stress responses. Sequence analysis of QTL markers or genes known to be associated with grain yield and salinity tolerance showed polymorphism in 20 genes, out of which nine were not previously reported. These candidate genes encoded Nucleotide-binding adaptor shared by APAF-1, R proteins, and CED-4 (NB-ARC) domain-containing protein, cyclase, receptor-like kinase, topoisomerase II-associated protein PAT1 domain-containing protein, ion channel regulatory protein, UNC-93 domain-containing protein, subunit A of the heteromeric ATP-citrate lyase, and three conserved hypothetical genes. Polymorphism was observed in the coding, intron, and untranslated regions of the genes on chromosomes 1, 2, 4, 7, 11, and 12. Genes showing polymorphism between the two genomes were considered as sequence-based new candidates derived from Oryza rufipogon for conferring high yield and salinity tolerance in IL50-13 for further functional studies.
RESUMO
In this study, we compared genome-wide transcriptome profile of two rice hybrids, one with (test hybrid IR79156A/IL50-13) and the other without (control hybrid IR79156A/KMR3) O. rufipogon introgressions to identify candidate genes related to grain yield in the test hybrid. IL50-13 (Chinsurah Nona2 IET21943) the male parent (restorer) used in the test hybrid, is an elite BC4F8 introgression line of KMR3 with O. rufipogon introgressions. We identified 2798 differentially expressed genes (DEGs) in flag leaf and 3706 DEGs in panicle. Overall, 78 DEGs were within the major yield QTL qyld2.1 and 25 within minor QTL qyld8.2. The DEGs were significantly (p < 0.05) enriched in starch synthesis, phenyl propanoid pathway, ubiquitin degradation and phytohormone related pathways in test hybrid compared to control hybrid. Sequence analysis of 136 DEGs from KMR3 and IL50-13 revealed 19 DEGs with SNP/InDel variations. Of the 19 DEGs only 6 showed both SNP and InDel variations in exon regions. Of these, two DEGs within qyld2.1, Phenylalanine ammonia- lyase (PAL) (Os02t0626400-01, OsPAL2) showed 184 SNPs and 11 InDel variations and Similar to phenylalanine ammonia- lyase (Os02t0627100-01, OsPAL4) showed 205 SNPs and 13 InDel variations. Both PAL genes within qyld2.1 and derived from O. rufipogon are high priority candidate genes for increasing grain yield in rice.
