The Expression Profiles Of OsPGIP Genes In Rice And The Function Of LRR Domain Of OsPGIP1

Polygalacturonase inhibiting protein(PGIP),a structural protein that specifically recognizing and binding to polygalacturonase(PG)produced by pathogenic agents,could block the PG to binding with host cell wall polysaccharide and inhibit its activity.In order to determine the expression profiles of OsPGIP genes in rice.RT-PCR was used to detect the expression levels of each OsPGIP gene in rice at different growth stages and in different stress conditions.Methods such as subcellular localization,fragment deletion,transient expression and pathogen inoculation were used to reveal the function of LRR fragments of OsPGIP 1.Results were as follows:1.The expression levels of OsPGIP genes were significantly different at different growth stages of the resistant cultivar YSBR1 and the susceptible cultivar Lemont.At seedling stage of YSBR1.the expression levels of OsPGIP3 and OsPGIP6 were the highest in the resistant cultivar YSBR1,while the expression levels of OsFOR1 and OsPGIP2 were the highest in rice at adult-plant and panicle stages.Except for OsPGIP2,the expression levels of all other OsPGIP genes at panicle stage were lower than that at adult-plant stage.Comparing to other OsPGIP genes in Lemont,the expression levels of OsFOR1 and OsPGIP6 were the highest at seedling stage of rice,and the expression levels of OsFOR1 and OsPGIP7were were the highest at adult-plant stage,while the expression levels of OsPGIP2 and OsFOR1 were the highest at panicle stage.2.The expression levels of OsPGIP genes were different under different stress conditions.Comparing to the control,the expression levels of OsFOR1 were up-regulated in the resistant and susceptible cultivars by 10.0 folds and 7.0 folds,respectively,while OsPGIP6 was only up-regulated in YSBR1.After being treated at 4 C,the expression levels of OsFOR1 were up-regulated by 15.7 folds and 5.4 folds,while OsPGIP4 and OsPGIP7 were only up-regulated in YSBR1 and Lemont,respectively.All OsPGIP genes were up-regulated in the plants of resistant and susceptible cultivars when the seedlings grew in the dark.However,the expression levels of all OsPGIP genes up-regulated in the plants were lower in the susceptible cultivar Lemont than that in the resistant cultivar YSBR1.For example,the expression levels of OsPGIP3 and OsFOR1 were up-regulated by 18.6 times and 13.0 times in YSBR1,while the expression levels of them in Lemont were only up-regulated by 2.5 times and 3.6 times.3.Results of subcellular localization showed that OsPGIP 1 was located in apoplast of the tobacco cell.A single LRR fragment deletion of OsPGIP 1 had no effect on its transport in plant cells,and 9 single LRR fragment deletions of OsPGIP 1 were all still located in apoplast.When the OsPGIP1 was transient-expressed in tobacco leaves,the spreading speed of Rhizoctonia solani,the pathogen of rice sheath blight,on the surface of treatment leaves was significantly lower than it on the control leaves.When the RsPG genes,such as RsPGl,RsPG2 and RsPG3,were transient-expressed in the tobacco leaves by agrobacterium transformation,the leaves transformed with RsPGl or RsPG3 showed apparent symptoms,but the leaves transformed RsPG2 not.When OsPGIP1 gene and its deletions were respectively transformed into tobacco cell with RsPGl gene at the same time,no symptoms showed in the tobacco leaves.It indicated that a single LRR fragment deletion of OsPGIP 1 did not affect its inhibiting activity to RsPG1.In summary,the expression levels of OsPGIP genes are significantly different in different rice cultivars at different growth stages and under different stress conditions.OsPGIP1 is localized in the apoplast of plant cell,and a single LRR fragment deletion does not affect its transport in plant cells.OsPGIP1 can inhibit the expansion of R.solani in the tobacco leaves and the activities of RsPGs.As well,a single LRR fragment deletion also had no effect on its inhibiting activity to RsPG1.