Physical interaction of RTBV ORFI with D1 protein of Oryza sativa and Fe/Zn homeostasis play a key role in symptoms development during rice tungro disease to facilitate the insect mediated virus transmission.

Rice tungro disease is caused by the combined action of Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). The RTBV is involved in the development of symptoms while RTSV is essential for virus transmission. We attempted to study the mode of action of RTBV in the development of symptoms. The tungro disease symptoms were attributed to viral interference in chlorophyll and carotenoids biosynthesis, photosynthesis machinery, iron/zinc homeostasis, and the genes encoding the enzymes associated with these biological processes of rice. The adverse effects of virus infection in photosystem II (PSII) activity was demonstrated by analyzing the Fv/Fm ratio, expression of psbA and cab1R genes, and direct interaction of RTBV ORF I protein with the D1 protein of rice. Since ORF I function is not yet known in the RTBV life cycle, this is the first report showing its involvement in regulating host photosynthesis process and symptoms development.