| FKF1and GI in Arabidopsis promote flowering in photoperiod flowering pathway mainly viaFKF1-GI-CDF1---CO-FT modules. In addition, FKF1and GI can activate FT expression directly orindirectly through other pathways in the regulation of flowering. Soybean is a typical short-day crop,and its sensitivity to photoperiod seriously limit the cultivated area of superior varieties. So study ofthe photoperiod-regulated flowering mechanism in soybean will play a important role in the extensionof planting and yield improving.In this study, we obtained FKF1and GI genes in soybean based on homology cloning method.Through proteins sequence alignment, similarity analysis and phylogenetic tree clustering, it wasverified that there were two FKF1copies and three GI copies in soybean, which were named GmFKF1,GmFKF2, GmGI1α, GmGI1β, GmGI2and GmGI3respectively. Of the total, GmGI1α and GmGI1βcame from one same gene with two different splicing manners.FKF1and GI proteins in soybean all mainly localized in nuclei in Arabidopsis protoplast, andsuggesting the subcellular localization pattern of FKF1and GI were conserved among various species.GmFKF1, GmFKF2and GmGI2had almost the same expression profiles in different tissue-organsand developmental stages, and had higher expression levels in short-day condition. GmGI1and GmGI3had similar expression profiles in different tissue-organs as GmGI2. However, GmGI1, GmGI2andGmGI3had day-length specificity in the expression profiles in developmental stages. FKF1and GI insoybean had maximum expression quantity in the second trifoliolate leaves at flowering stage, and hadhigher expression level in flower under long-day condition and in root under short-day condition.Therefore, FKF1and GI in soybean may function in the same tissue-organs or the samedevelopmental stage. Moreover, the functional tissue-organs may be different owing to differentphotoperiod condition.GmFKF1, GmFKF2and GmGI2had almost identical circadian expression profiles under differentday-length conditions and mainly regulated by the circadian clock, meanwhile light also affected theircircadian expression profiles. GmGI1and GmGI3had different circadian expression profiles withweaker oscillating rhythm and unstable cycle periods. Light played a much greater role than circadianclock in the regulation of circadian expression of GmGI1and GmGI3. The robust oscillation expressionof FKF1and GI in soybean did not became disorder immediately under photoperiod transition.GmFKF1and GmFKF2respectively interacted with GmGI1, GmGI2and GmCDF2in yeast.GmGI1and GmGI2had an interaction with GmCDF2. The total length of GmGI3protein did not had aninteraction with GmFKFs and GmCDF2, but the N terminal of GmGI3had stronger interaction withGmFKFs and GmCDF2. The N terminal of GmFKFs, GmGI2and GmGI3were mainly responsible forinteraction among the same kinds or different kinds of proteins, while the N terminal of GmGI1primarily mediated the interaction among the same kinds of proteins. GmFKF1and GmFKF2could notform homology or heterology dimmers, while the N terminal of GmFKF1and GmFKF2interacted with each other. GmGI1, GmGI2and GmGI3interacted with each other. The interaction above in yeast wasindependent of light. Therefore, the interaction manners among FKF1, GI and CDF2had conservatismand specificity in different species.In long days, the transgenic plants of over-expression GmFKF1in Arabidopsis flowered earlierthan WT, while GmFKF2flowered normally as wild-type Col0indicating by either days to flowering orthe total rosette leaf number at flowering. While in short days, more than fifty percent plants of eitherover-expression GmFKF1or GmFKF2flowered much earlier than wild type. There was a significantdifference in branch numbers between the transgenic plants of co-overexpression GmFKF1andGmFKF2and the wild type. GmGI1may had a role in plant vegetable growth, and had little effect onflowering time. So the action of FKF1and GI in soybean may be special.
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