Analysis Of COL7and FOF1in Regulating Arabidopsis Development

During the whole life of Arabidopsis thaliana, the transition of vegetative growthto reproductive growth is controlled by both inner and outside signals. CONSTANS(CO) plays a key role in photoperiod and intergrates the signals of light, temperature,and clock to regulate flowering. In Arabidopsis there are17CONSTANS-LIKEs (COLs)family genes. So far the functions of most of COLs are still unknown. FT is thedownstream gene of CO, which can directly bind the promoter of FT and initiate thetranscription of FT. The blue light receptor CRY2(CRYPTOCHROME2) isphotolyase-like flavin proteins, mediating various light responses in plants. Therecently studies show that CRY2initiates FT transcription by blue light specificallyinteracting with CIB1(CRYPTOCHROME-INTERACTION BASICHELIX–LOOP–HELIX1). CIB1proteins are stable in blue light but unstable withoutblue light, which is degradated through26S proteasome. FOF1(F-BOX OFFLOWERING1) is a PP2(Phloem Protein2) E3protein which contains a F-boxdomain. FOF1can speed the degradation of CIB1. ZTL (ZEITLUPE) can inhibit theactivity of FOF1to stable CIB1. Our studies include the researches of COL7andFOF1. Through the studies of COL7and FOF1, we made the following coclusions:(1) COL7suppresses the CO and FT transcription to delay Arabidopsis flowering.(2) The first discovered that COL7affects plant branching. Overexpression ofCOL7under low density and high R/FR ratio condition can increase the plant branches,but the high density and low R/FR ratio condition can inhibit the plant branching.Compare to the WT, col7mutant has shorter hypocotyl under the low R/FR ratio andCOL7-OX has longer hypocotyl. COL7is the positive regulator of PIL1which is themarker gene of SAS (shade avoidance syndrome). So COL7promters branching andenhances SAS in response to low R/FR.(3) COL7inhibit the synthesis of anthocyanin and chlorophyll under the blue,particularly evident under salt stress.(4) We first discovered that FOF1(F-BOX OF FLOWERING1) is involved inflowering regulating. Overexpression of FOF1can cause late flowering. The fof1mutant has no flowering phenotype but the fof1-cs (co-suppress) lines have obviouslyflowering phenotype. The datas show that FOF1may have redundant functions withPP2-B family genes in controlling flowering. FOF1regulates flowering time by inhibiting FT rather than CO.(5) The interations between FOF1and CIB1are proved by yeast two hybrid,CO-IP, Spli-LUC.(6) FOF1is the E3of CIB1.(7) CIB1protein is stable under the blue light but not stable without blue light. Inthe ztl-3and ztl-21mutants, CIB1protein will not stable under the blue light. So bluelight stabilizes CIB1required ZTL. ZTL can interact with FOF1in vivo and in vitro,so ZTL may stabilize CIB1by inhibiting the E3activity of FOF1.