The CTD Phosphorylation Of RNA POL? Largest Subunit (RPB1) Regulates The Flowering Time And Shoot Apical Meristem Activity In Arabidopsis

The growth and development of plant include embryonic and post-embryonic development.It is specially that most plant organs are derived from the post-embryonic development.In the post-embryonic development,the two distal apical meristems determine the morphogenesis of whole plant.We obtain a Constitutive Auxin Response mutant with the DR5::GFP(card1-1)from EMS mutagenesis screening.A G-to-A base substitution was found in the C terminal domain of largest subunit RPB1 of RNA Pol II,which caused mRNA splicing error and truncated CTD domain of RPB1.In Arabidopsis,RPB1 CTD contains 40 highly conserved tandem repeat sequences Tyr-Pro-Ser-Thr-Ser-Pro-Ser,while the card1-1 mutant has a shortened CTD terminated at the thirty-second repeat.The card1-1 mutant has globe phenotypes in the process of the plant growth and development,such as more rosette leaves and flower organs,shorter roots and longer hypocotyls.Also,the flowering time of card1-1 is later than the wild type.The changed posphorylation level of CTD with distinguished different expression level of FLC and FT were found in RPB1 mutants.It is suggested that the different phosphorylation status of CTD may control the flowering time through regulating the expression of FLC and FT.The shoot apical of card1-1 is larger than WT and clv3-2/card1-1 double mutant has synergistic effects compared with clv3-2 single mutant.It indicates that the phosphorylation status of CTD also play an important role in maintenance of apical meristem activity.Moreover the responses of card1 mutants to various hormones are different from the wild type,such as less sensitive to abscisic acid,6-BA and more sensitive to ACC,GA3.So It is possibly that the endogenous and environments signal can finely regulate the response genes transcription by integrating control RPB1 CTD phosphorylation in plant.