ZmPGIP1 regulates stem strength by enhancing lignin and cellulose biosynthesis in Arabidopsis thaliana

Polygalacturonase inhibiting proteins (PGIPs) are typical leucine-rich repeat (LRR) proteins that inhibit the activity of polygalacturonase (PG) in pathogens, but their function in promoting to plant stem development has been less studied. In this study, the PGIP gene from Zea mays was cloned and heterologously expressed in Arabidopsis thaliana, and then the plant phenotypes were observed and a set of physiological and biochemical indicators were measured. The results indicate that the ZmPGIP1 protein is expressed both in the cell membrane and cell wall. Our research observed that the heterologous expression of ZmPGIP1 significantly increased the production of lignin, cellulose and hemicellulose in transgenic lines. The stems of transgenic plants also showed a thicker cortical tissue. The increase in lignin deposition observed during histochemical staining suggests that the ZmPGIP1 gene may improve plant mechanical strength. These were tightly associated with the upregulated expression of lignin/cellulose-synthesis genes (C4H, C3H, F5H, PAL1/3, CCR1, CAD1-3/9, CCOMT, MYB58, CESA1/10) to enhance plant cell wall strength in transgenic lines. Our findings provide new perspectives on the growth regulation mechanisms of PGIP proteins in plant cell walls and provide a potential candidate gene for breeding increased disease-resistance and higher cellulose production in plants.