Expression Analysis And Genetic Transformation Of OsHSP Genes In Rice

Abiotic stresses,such as drought,salinity,extreme temperatures,and oxidative stress, adversely affect plant growth and development and final crop yield performance.It is of great importance to find stress related genes,to reveal the molecular mechanisms of stress tolerance and to improve stress resistance of crops in modern crop breeding programs.Heat shock proteins(HSPs) are a group of proteins whose expression is increased when the cells are exposed to elevated temperatures or other stress.Increased expression of these proteins can protect the organism against stress-induced damage.In this study,nine OsHSP genes in rice(Oryza sativa L.) were studied for their expression levels under several stress conditions and in different tissues.Plant expression vectors of these nine OsHSP genes were constructed and transferred into the rice separately via Agrobacterium-mediated transformation.The main results are as following:1.Semiquantitative RT-PCR method was used to study the expression level of nine OsHSP genes in six different rice tissues including root,stem,leaf,sheath,young spike and germinating embryo.The nine OsHSP genes examined in this study exhibited differential spatiotemporal expression.These observations indicate that different OsHSP proteins may play certain roles in plant development.2.Effects of environmental stresses,including heat,cold,high salt,drought and ABA on the expression of OsHSP genes were analysised by semiquantitative RT-PCR.All nine OsHSP genes were affected by heat shock while unaffected by cold.The expression of OsHSP80.2,OsHSP71.1 and OsHSP23.7 was induced by salt.OsHSP80.2 and OsHSP24.1 were induced by drought treatment.Interestingly,OsHSP71.1 was induced by ABA,while OsHSP24.1 was repressed by ABA.Collectively,these observations revealed that the OsHSP genes respond to different abiotic stresses via an ABA-independent or an ABA-independent pathway.3.Plant expression vectors including nine over-expression vectors and two RNAi vectors were constructed,and then 6 OsHSP over-expression vectors and 2 OsHSP RNAi vectors were transferred into the rice separately via Agrobacterium-mediated transformation.Hybromycin-resistant rice plantlets were obtained from 5 over-expression vectors,12 positive lines of OsHSP71.1-OE and 6 positive lines of OsHSP23.7-OE were detected by PCR and shown higher expression by semiquantitative RT-PCR.