Cryptochrome Mediated Blue Light And ABA Signaling Regulates Gemma Dormancy In The Novel Model Plant Marchantia Polymorpha

Light as one of the most important external environmental factors in the plant growth,almost affects the development of the entire life cycle from seed germination to aging and death.Among them,cryptochromes(CRYs)are mainly as blue light receptor to absorb blue light.CRY1 and CRY2 are the two cryptochrome proteins in model plants Arabidopsis thaliana,and the light signal transduction mechanism of them is the most deeply studied.Recently,studies have reported that CRYs proteins can also participate in hormone signaling pathways to inhibit hypocotyl elongation.In addition to Arabidopsis thaliana,CRYs proteins in other plants mediate specific molecular function.However,their molecular mechanisms have not been thoroughly studied.Marchantia polymorpha is a new model plant that has emerged in recent years.It is the first plant to grow on the land during the evolution of plants terrestrialization.In view of the evolutionary status of Marchantia polymorpha in plants and its low gene redundancy,the objects of this study have focused on Marchantia polymorpha to broaden the understanding of cryptochromes function in plants by means of deeply analyzing the mechanism of cryptochrome-mediated blue light signal transduction.In this study,we used molecular biology techniques such as gene editing to obtain MpCRY mutations and over-expression transgenic lines.And then,we planted these transgenic plants in various light conditions for treatment to observe their physiological phenotypes and test the biochemical characteristics of MpCRY protein.Based on these preliminary results,we found MpCRY regulated ABA signaling related genes,and initially established a MpCRY co-mediated gene expression regulatory network in response to the blue light and ABA signaling pathways.The main findings are as follows:1.We identified the single-copy cryptochrome gene MpCRY from the Marchantia polymorpha.Protein structure and phylogenetic analysis revealed that MpCRY has a conserved PHR domain of plant cryptochrome and its own specific CCE domain,which is likely to be the ancestor of the existing land plant cryptochrome.Protein characteristic analysis found that MpCRY protein undergo blue light-specific dimerization,phosphorylation and degradation.At the same time,the expression of MpCRY gene was inhibited by blue light.Subcellular localization analysis revealed the blue light-induced MpCRY protein transferring from the cytosol to the nucleus,which was specific mechanism in Marchantia polymorpha.2.The phenotypic observation of the blue light treated transgenic Marchantia polymorpha plant reveal that MpCRY has multiple functional characteristics.It affected the growth and development of the thallus and promoted the transition of their growth status from vertical to horizontal;MpCRY also promoted the growth and development of the gemma rhiziods which located in or outside the gemma cup.It also could inhibit the dormancy of gemma and promoted its germination and growth;MpCRY affected its sexual reproductive growth by inhibiting the gametangiophore formation.3.Further research on the dormancy of gemma revealed that,under blue light conditions,MpCRY regulates the expression of the abscisic acid signaling regulated genes such as MpABI3 A to inhibit the positive response of ABA responsive genes such as MpLEA1 in response to ABA signals,resulting in further weakened the inhibition effect of ABA on the growth and germination of gemma.The above research results revealed that,the single-copy cryptochrome protein MpCRY in Marchantia polymorpha undergoes the blue light induced nuclear localization,dimerization and phosphorylation to increase its activity,and the activated MpCRY participates in the ABA signaling pathway to regulate the dormancy and germination of gemma.