Overexpression of Non-Photochemical Quenching (NPQ) Related Genes Alters Plant Development and Enhances Plant Osmotic Stress Resistance in Creeping Bentgrass

Photosynthesis, an important pathway for plants to accumulate organic matters, is critical for plant productivity. This process transforms the carbon dioxide and water into carbohydrates and releases oxygen. However, when the light intensity is too high, more reactive oxygen species (ROS) is generated in the photochemical reaction center, leading to the photodamage of plants. Plants have evolved different photoprotection mechanisms, such as Non-photochemical Quenching (NPQ), to prevent this damage at the expense of photosynthetic rate. NPQ converts excess light energy into heat energy and dissipates it, avoiding damage to plants under excessive light. Overexpression of photoprotection proteins violaxanthin de-epoxidase (VDE), zeaxanthin epoxidase (ZEP) and photosystem II subunit S protein (PsbS), should accelerate the induction and relaxation rate of NPQ, resulting in increased biomass production. This strategy has previously been reported in dicot species tobacco (Nicotiana tabacum) with 15% increase in dry weight. This project is focused on monocot species creeping bentgrass (Agrostis stolonifera L.) to examine the feasibility of applying the similar strategy in monocot crop plants. OsaVPZ genes were cloned from rice (Oryza sativa), then introduced into creeping bentgrass to generate overexpression transgenic plants to study whether the same mechanism of photoprotection can be triggered and to explore possible biological roles of these genes in plant stress regulation. Our preliminary experimental results revealed inhibited plant development in OsaVPZ lines grown under 400 μmol m-2s-1 photosynthetically active radiation (PAR), and this suppression in plant development was mitigated when PAR reached at 700 μmol m-2s-1. Transgenic plants also exhibited significantly higher drought resistance and faster recovery from salinity stress than wild type controls. Further characterization of the transgenic plants would reveal whether the rapid decline of NPQ process would reduce energy dissipation to increase plant productivity, and allow a better understanding of the function of these three genes involved in osmotic stress