A group III patatin-like phospholipase gene pPLAIII regulates lignin biosynthesis and influences the rate of seed germination in Arabidopsis thaliana

The lignification of plant secondarywalls is an important process that provides plants with mechanical support. However, the presence of lignin in the secondary walls affects the readily availability of cellulose required in various industries, including the biofuel, paper, and textile industries. Thus, plants with less lignin are ideal for usage in such industries. Molecular studies have identified genes that regulate plant lignification, including group III plant-specific patatin-related phospholipase genes. Recent studies have reported decreased lignin content when pPLAIII alpha, pPLAIII gamma (from Arabidopsis thaliana), and pPLAIII beta (from Panax ginseng) were overexpressed in Arabidopsis. However, the role played by a closely related gene pPLAIII delta in lignin biosynthesis has not yet been reported. In this study, we found that overexpression of the pPLAIII delta significantly reduced the lignin content in secondary cell walls, whereas the silencing of the gene increased secondary walls lignification. Transcript level analysis showed that the key structural and regulatory genes involved in the lignin biosynthesis pathway decreased in overexpression, and increased in plants with silenced pPLAIII delta. Further analysis revealed that pPLAIII delta played an influential role in several physiological processes including seed germination, and chlorophyll accumulation. Moreover, the gene also influenced the size of plants and plant organs, including leaves, seeds, and root hairs. Generally, our study provides important insights toward the use of genetic engineering for lignin reduction in plants and provides information about the agronomical and physiological suitability of pPLAIII delta transgenic plants for utilization in biomass processing industries.