Genome-Wide Identification and Analysis of Biotic and Abiotic Stress Regulation of C Photosynthetic Pathway Genes in Rice.

Photosynthetic fixation of CO is more efficient in C than in C plants. Rice is a C plant and a potential target for genetic engineering of the C pathway. It is known that genes encoding C enzymes are present in C plants. However, no systematic analysis has been conducted to determine if these C gene family members are expressed in diverse rice genotypes. In this study, we identified 15 genes belonging to the five C gene families in rice genome through BLAST search using known maize C photosynthetic pathway genes. Phylogenetic relationship of rice C photosynthetic pathway genes and their isoforms with other grass genomes (Brachypodium, maize, Sorghum and Setaria), showed that these genes were highly conserved across grass genomes. Spatiotemporal, hormone, and abiotic stress specific expression pattern of the identified genes revealed constitutive as well as inductive responses of the C photosynthetic pathway in different tissues and developmental stages of rice. Expression levels of C specific gene family members in flag leaf during tillering stage were quantitatively analyzed in five rice genotypes covering three species, viz. Oryza sativa, ssp. japonica (cv. Nipponbare), Oryza sativa, ssp. indica (cv IR64, Swarna), and two wild species Oryza barthii and Oryza australiensis. The results showed that all the identified genes expressed in rice and exhibited differential expression pattern during different growth stages, and in response to biotic and abiotic stress conditions and hormone treatments. Our study concludes that C photosynthetic pathway genes present in rice play a crucial role in stress regulation and might act as targets for C pathway engineering via CRISPR-mediated breeding.