The Influence Of Rice Grassy Stunt Virus On Rice Potassium Metabolism

Rice, which is the most important crop in the world, is subject to viral diseases in recent years. Rice grassy stunt virus (RGSV), the type species of Tenuivirus, had a large area outbreak in South Asia and Southeast Asia and caused severe damage to rice production. To study symptoms like brown or rust-colored spots with irregμLar shape on the rice leaves infected by RGSV, pathogenic mechanisms of RGSV was analyzed.In this study, the potassium was detected in rice (cv. TN1 and Nipponbare)infected by RGSV, respectively. Using the healthy rice as control, potassium content of TN1 and Nipponbare was reduced by 52% and 36%, respectively. The results showed that the absorption of potassium ions in rice was significantly inhibited after infected by RGSV. And this inhibitory effect is different between different rice cultivars with relevant resistance The more susceptible the rice varieties, the more significantly affected by the virus. Our results suggest that rust-colored spots on RGSV infected rice leaves might be related to the suppression of absorption of potassium by virus.In this study, we analyse transcriptional level of 59 genes related to rice potassium ion absorption by real time PCR. The results showed that 8 genes displayed a higher transcriptional level:including OsCIPK25, OsCIPK5, OsCBL5 and OsCBL7 which belong to plant stress response signal system CBL/CIPK, Na+/K+ transporter protein OsHKT1;5, high-affinity potassium transporter OsHAK23 (Os09g21000), rice gene Os01g0782700 homologous to Arabidopsis cyclic nucleotide gated ion channels AtCNGC4 which can transport Na+/K+ and have resistant function, high efficiency transport channel protein OsAKT2/3. When rice was infected by RGSV, absorption of potassium ion was inhibited, while transcriptional level of transport protein associated with potassium ion was up-regulated. Our results revealed that infection of RGSV might inhibit the translational level or protein activity of potassium ion associated transport protein, on the other hand, the plant stress response up-regulated the transcriptional level of the corresponding genes.Based on the above analysis, genes of CBL/CIPK family, OsHKT1;5(SKC1) and OsHAK23 were chosen to be further studied. To confirm relationship between grassy disease symptoms and potassium, over-expression and RNA silencing of such genes in rice were conducted, which could deepen our understanding of RGSV pathogenesis. In this study, we constructed plant over-expression vectors of OsCBL5, OsCBL7 and RNAi vectors of Os09g21000,OsCBL5, OsCIPK5 and OsHKT1;5. Via Agrobacterium-mediated transgenic systems, all the above genes were individually transformed into rice plants. Our study provide meaningful materials for the further research on pathogenic mechanisms of RGSV.