Genetic Mechanisms Of QPE9-1 For Panicle Erectness In Rice

Rice is one of the most important food crops in China.Increasing rice grain yield per unit is the effective strategy to ensure food safety.Nowadays,the utilization of heterosis combing with ideal plant type is thought to be an important strategy to achieve a yield leap in the future.Most of the japonica rice varieties grown today in China are of the panicle erectness(PE)type.Although the key gene,qPE9-1,determining panicle erectness was cloned,the mechanism still remains elusive.In previous research,we screened out one protein PIP1(qPE9-1 Interacting Protein 1),which interacted with qPE9-1 and belongs to GASR family,using two yeast-hybrid method.RNAi transgenic lines of PIP1 were generated.Based on these studies,we continued carrying out a series of related works to uncover the molecular basis of panicle erectnessin rice.The main results are as follows:1.Three different truncated qPE9-1 protelin including Gy domain,G? and TM domain,TM and Cys-rich domain were fused with pGBKT7(BD)vector,respectively.And PIP1 was fused with pGADT7(AD).Yeast two hybrid assays indicated that PIP1 interact with the cys-rich domain of qPE9-1 C-terminal,but failed to interact with the G? domain.2.We obtained two homozygous RNAi transgenic lines,PIP1-RNAil and PIP1-RNAi2,in T2 generation and investigated several important agronomic traits.The results indicated that the plants with lower expression level of PIP1 showed reduced plant height,shorter panicle length and decreased grain number per panicle.Additionally,flag leaf length,flag leaf width and seed size of PIP1-RNAil and PIP1-RNAi2 were also declined.However,there is no significant difference in panicle number per plant was observed between transgenic lines and wild type.3.Using the second leaf sheath length as a standard,we detected the response of transgenic lines to GA3.Both of the PIP1 and qPE9-1 RNAi lines showed decreased sensitivity to GA3,while the complementary lines of qPE9-1 exhibited enhanced sensibility to GA3.These results revealed that PIP1 and qPE9-1 are positive regulatory factors to GA3 response.These two genes may control plant height,panicle length and grain size,and shape PE type plant architecture by regulating the response to GA3 rice.4.We also generated several mutants of qPE9-1 and PIP1 using CRISPR/Cas9 system.Sequencing analysis showed that some homozygous TO mutants with nucleotide insertion and deletion of qPE9-1 and PIP1 were obtained,which provides important materials for further study on biological function of qPE9-1 and PIP1.