Functional Analysis Of Polygalacturonase Inhibiting Protein Gene ZmPGIP3 To Resistance Against Rice Sheath Blight

Plants are continually exposed to adverse environments,including abiotic stresses such as drought,salinity and low temperature,and biotic stresses resulting from pathogen and pest attack.Rice(Oryza sativa)is a staple food crop for the human population,as more than 50%of the world's population is dependent on the rice for the majority of its food requirements.As with many other crops,a large number of pathogenic microorganisms cause important diseases in rice,leading to significant yield losses worldwide and threatening global food security.Plant polygalacturonase inhibitory protein(PGIP)is a structural protein capable of specifically recognizing and binding fungal polygalacturonase(PG),which is rich in leucine repeat(LRR)structure.It plays an important role in plant antifungal diseases.In this study,the ZmPGIP3 gene was cloned by PCR.It was found that the gene has an LRR domain by sequence alignment,and there is a hydrophobic N-terminal signal peptide structre and a pair of conserved cysteine residues,preliminarily considered to be corn PGIP family genes.Further comparative analysis revealed that this gene is highly homologous to OsPGIP1 in rice.Phylogenetic analysis also showed that the gene is closely related to OsPGIPl,and it was identified as a maize PGIP family gene,named ZmPGIP3.Subcellular localization shows that ZmPGIP3 is located in the cell wall or cell membrane,quantitative real-time PCR showed that ZmPGIP3 was expressed in roots,stems,leaves,stamens,pistils,and seeds of maize,with the highest expression in roots.After the stress treatment,it was found that ZmPGIP3 was significantly induced by wounding,SA,JA and NaCl.It is speculated that ZmPGIP may be related to disease resistance and may participate in plant disease resistance regulation through the JA or SA pathway.In order to further verify the gene function of ZmPGIP3,a ZmPGIP3 expression vector was constructed.ZmPGIP3 was transferred into rice by Agrobacterium-mediated method,and pure line plants were obtained.Fluorescent quantitative PCR showed that ZmPGIP3 was expressed in transgenic plants.Studies on inoculation with rice germs showed that resistance to rice sheath blight and rice blast disease was obtained after ZmPGIP3 was transferred to rice,and the infected area of transgenic plants was much lower than that of wild-type control plants.Therefore,it is believed that ZmPGIP3 can enhance rice resistance to sheath blight and rice blast.In order to clarify the mechanism of disease resistance of transgenic rice,defensive gene expression in rice after inoculation was measured?Fluorescence quantitative PCR results showed that overexpression of the gene ZmPGIP3 enhanced JA pathway-associated stress response genes(AOC and AOS).This indicates that ZmPGIP3 regulates rice sheath blight resistance and rice blast disease through the JA pathway.