Study on the Rna Helicase 42 in Cold-Induced Pre-Mrna Splicing Mechanism in Rice(2/3)

Rice (Oryza sativa) is among the most important crops in the world, and is the main staple food for almost 50% of the world’s population. As a tropical and subtropical crop plant, rice is sensitive to cold stress. RNA molecules, including mRNA, rRNA, and tRNA, perform a specific function based on their well-defined structure during gene expression. Low temperature causes over-stabilization of incorrectly folded RNA and therefore leads to RNA molecular inactivation. RNA chaperones and RNA helicases function to ensure formation of mature RNAs of the correct structure by means of their RNA unwinding and RNA unfolding activities. RNA helicases are enzymes that can rearrange ribonucleoprotein (RNP) complexes and modify RNA structures, and are therefore involved in all aspects of RNA metabolism. DEAD-box helicases, which constitute the largest family of RNA helicases, exhibit variable protein sizes and compositions of N- and C-terminal extension sequences. Previously, we demonstrate that the rate of pre-mRNA splicing is reduced in rice at low temperatures, and the DEAD-box RNA helicase 42 (OsRH42) is necessary to support effective splicing of pre-mRNA during mRNA maturation at low temperatures. OsRH42 expression is tightly coupled to temperature fluctuation, and OsRH42 is localized in the splicing speckles and interacts directly with U2 snRNA. Retarded pre-mRNA splicing and plant growth defects were exhibited by OsRH42-knockdown transgenic lines at low temperatures, thus indicating that OsRH42 performs an essential role in ensuring accurate pre-mRNA splicing and normal plant growth under low ambient temperature. Unexpectedly, our results show that OsRH42 overexpression significantly disrupts the pre-mRNA splicing pathway, causing retarded plant growth and reducing plant cold tolerance. Combined, these results indicate that accurate control of OsRH42 homeostasis is essential for rice plants to respond to changes in ambient temperature. In addition, our study presents the molecular mechanism of DEAD-box RNA helicase function in pre-mRNA splicing, which is required for adaptation to cold stress in rice. However, it is important to understand the detail molecular mechanism of the OsRH42 function in cold stress resistance in rice. Therefore, the interaction proteins of the OsRH42 and the pre-mRNA targets of OsRH42 will be elucidated. Furthermore, inducible overexpression of OsRH42 in transgenic rice plants will be tested for their adapt ability under cold stress. Combining the results from these studies, we will have knowledge in OsRH42-mediated cold tolerance pathway and to develop a cold stress tolerant rice plants.