Functional Analysis Of OsPGIP1 And OsPGIP4 To Resistance Against Xanthomonas Oryzae Pv. Oryzicola In Rice

Rice is an important food crop in China. Bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv.oryzicola, becomes the main destructive bacterial disease of rice in some area of China with its heavy severity. However, there has only reported to character a few quantitative trait loci (QTLs) without any qualitative resistance genes in rice.Among them, qBlsr5a, located on the short arm of chromosome 5, was reported as the largest effect of QTLs for BLS resistance. On the other hand, denfese-related (DR) genes were frequently used to explain the function of rice resistance QTLs. And it was very important to mine and utilize the DR genes for breeding the BLS resistance rice. Because the chromosomal location of OsPGIP1 and OsPGIP4 are coincided with the qBlsr5a, the major bacterial leaf streak resistance QTL, we analyzed the function of OsPGIP1 and OsPGIP4 to resistance against Xanthomonas oryzae pv.oryzicola in this studies.OsPGIPl and OsPGIP4 were up-regulated expression within 8h upon pathogen inoculation with Xanthomonas oryzae pv. oryzicola strain RS105 both in susceptible rice variety Zhonghua 11 and moderate resistance variety Acc8558. And the activated fold post 8 h inoculation is higher in resistance variety Acc8558 than in Zhonghua 11. It suggested that OsPGIP1 and OsPGIP4 may participate in the resistance process against Xoc. The expression profile of OsPGIP1 and OsPGIP4 in different tissue and organ were detected by quantitative RT-PCR in Zhonghua 11 too. The expression level of OsPGIP1 and OsPGIP4 is higher in leaf. We cloned OsPGIPl and OsPGIP4 from BLS moderate resistant variety Acc8558. After sequence the alleles of OsPGIP1 and OsPGIP4 in susceptible rice Zhonghuall and resistance rice Acc8558. The allele of OsPGIP1 in Zhonghua 11 and in Acc8558 is complete same as annotation in Nipponbare, the rice finished the genomic sequence. But there has 7 nucleotides differences which has resulted in two amino acid substitutions between Zhonghua 11 and Acc8558 for OsPGIP4. The vectors for both overexpression and RNAi were constucted for the OsPGIP1 and OsPGIP4 respectively. In To generation, whatever overexpression of OsPGIP1 or OsPGIP4 could enhance the resistance against RS105 in Zhonghua 11, and repressing the expression of OsPGIP1 or OsPGIP4 could enhance more susceptibility to RS105. In T1 generation, the cosegregation analysis was consisted with in To generation. These results suggested that OsPGIP1 and OsPGIP4 act as a positive regulator to resistance against Xoc in rice.Quantitative real-time PCR was used to measure the basal levels of transcripts for several pathogenesis-related genes in three OsPGIP4 overexpression lines and wild-type. OsPR1a and OsPR1b, represented as the markers of SA-dependent pathway, were shown to be significantly reduced in all three OsPGIP4 overexpression lines at 24 hpi as compared with the wild-type. On the contrary, all three OsPGIP4 overexpression lines showed significantly higher expression of OsAOC and OsAOS which represented as the markers of JA-dependent pathway. These results were implied that OsPGIP4 may participate in the BLS resistance dependent on JA pathway.OsPGIPl and OsPGIP4 were predicted to encode putative PGIP protein. They were identified to efficiently resistant against fungal pathogens in rice. Our results not only provide the fist reported that rice PGIP protein could resistant against a bacterial pathogen, but also indicate that OsPGIP1 and OsPGIP4 are potentially a candidate component of qBlsr5a locus for bacterial leaf streak in rice.