Plant growth, biomass production, and potential yield are negatively affected by abiotic stresses such as drought and salinity. These stresses affect agricultural production in many countries, causing multi-million dollar losses for farmers, the agricultural industry and resulting in poverty worldwide. Incidences of both drought and salinity stresses are increasing due to the effects of climate change, while enhanced stress tolerance of important crops is a complex task. It has therefore been proposed that stress tolerance may be better targeted by‘designing’ better varieties of crop plants. Whilst many reports have shown that over-expression of some stress-inducible genes in transgenic plants can improve drought and salinity tolerance. However, these studies are relatively limited in important crop plants. Lipids such as phosphatidic acid (PA) and LysoPA have been shown to be important messengers to regulate drought and salt stress. Lysophosphatidic acid acyltransferase2 (LPAT2) catalyzed the de novo synthesis of PA in cells. The role of LPAT2 in plant osmotic stress is still unclear. This study aimed to explore the role of LPAT2 response to hyperosmotic stress and abscisic acid (ABA). The main findings from this study are as following:1. Rice LPAT2 transcript is existing in all tissues tested with relatively higher in leaves and roots, and was induced by salt, drought and ABA treatment, suggesting its roles in plant growth and stress response. Moreover, LPAT2 is localized to the endoplasmic reticulum (ER) membrane, implicating its role in lipid metabolism and signaling.2. Rice LPAT2 might be essential for gametophyte or embryo development as homozygous mutant for a T-DNA insertion in LPAT2 coding region fails to recover in rice.3. A knockdown mutant lpat2 with a reduced transcript level of LPAT2 was isolated from rice, which provides a possibility for function characterization of LPAT2 in post-embryo study.4. Using a knockdown mutant lpat2 and its genetic complementation revealed that LPAT2 is important for plants to adapt osmotic stress. Reduced LPAT2 conferred plants and seeds were more sensitive to ABA treatment, and were less tolerant to salt and drought stress. The results suggest that LPAT2 play a positive role in ABA response and stress tolerance.5. The role of LPAT2 in osmotic stress is mediated by ABA response as shown that the lpat2 mutant exhibited more water loss from leaves when supplied ABA under salt stress. The ABA responsive gene RAB18 was less induced by ABA and salt in the lpat2 mutant. The result suggests that LPAT2 enhance ABA response to promote plants osmotic stress tolerance.6. PA produced by LPAT2 activity might be also important for ABA response. PA supplementation is capable of restoring ABA sensing and salt stress tolerance as WT performance.7. The effects of LPAT2 on plant stress tolerance might be dual effects of PA, enhanced ABA response.