Function Of ABI4 In Photomorphogenesis And Flowering Time Regulated By CRY2 In Arabidopsis Thaliana

Plants have evolved a variety of photoreceptors to perceive specific wavelengths of light in the environment,and cryptochromes(CRYs)are class of blue/UV-A light receptors mediating blue light signal transduction and many aspects of plant growth and development.CRY2 plays important roles in promoting photomorphogenesis and photoperiodical flowering in Arabidopsis.ABI4(ABA INSENSITIVE 4)is an AP2/ERF domain-containing transcription factor,which plays key regulatory roles in seed dormancy and germination,seedling photomorphogenesis,and plant floral transition.In this study,the loss-of-function mutants of ABI4 and CRY2,in the Columbia(wild-type,WT)background,were used to generate the double mutant cry2abi4 through hybridization.The photomorphogenic phenotypes of four genotypes were identified under different intensity of blue light.The results showed that the hypocotyl length of the abi4 mutant was significantly shorter than that of the WT,which was consistent with the previous study;while the hypocotyl length of the cry2abi4 double mutant was similar to that of the cry2,which was significantly longer than that of the WT,indicating that the light-sensitive phenotype of the abi4 mutant is caused by the enhanced function of CRY2.ABI4 inhibits the function of CRY2 to inhibit photomorphogenesis.CRY2 is the downstream protein of ABI4,and CRY2 is the epistasis gene of ABI4.Further studies showed that in the abi4 mutant,the degradation of CRY2 becomes slower,COP1(constitutive photomorphogenic 1,COP1)promotes the interaction between ABI4 and CRY2,and ABI4 constitutively promotes the formation of CRY2 dimers,indicating that ABI4 may regulate the formation of CRY2 dimers to regulate the function of CRY2.The flowering time of four genotypes of Arabidopsis thaliana was identified,and the flowering time of abi4 was earlier than that of WT,which was consistent with the previous study,while the flowering time of cry2abi4 was consistent with that of cry2,suggesting that ABI4 also plays an inhibitory role in the flowering transition regulated by CRY2.Specific research results are as follows:1.Under weak blue light conditions,the hypocotyl length of the cry2 was significantly longer than WT,and that of the abi4 was significantly shorter than WT.The hypocotyl length of cry2abi4 is consistent with cry2,indicating that ABI4 inhibits hypocotyl elongation in Arabidopsis thaliana by inhibiting the function of CRY2,and CRY2 is the epistasis gene of ABI4.2.CRY2 can interact with ABI4,and COP1 promotes the interaction between CRY2 and ABI4.3.ABI4 promotes the degradation of CRY2 under blue light,and ABI4 constitutively promotes the formation of CRY2 dimers,indicating that ABI4 may affect the degradation of CRY2 by interfering with the formation of CRY2 dimers.4.The flowering time of abi4 was earlier than that of WT,and the flowering time of cry2abi4 was the same as that of cry2,which was later than that of WT,indicating that ABI4 also played an inhibitory role in the promotion of Arabidopsis thaliana photoperiodical flowering by CRY2.