Blue Light Induced Arabidopsis CRY2 Dimerization And Regulation

CRYs are flavin-binding blue light receptors. All CRYs share sequence similarity at their N-terminal photolyase-related domain(PHR) with DNA photolyases, and they act as photoreceptors not only in plants, but also in bacteria, insects, coral, zebrafish, chicken, and mammal C-terminal domain is considered to be a unique extension of cryptochrome(CCE), the region shows a high degree of variability, unstructured, but for the essential elements of the function cryptochrome. Arabidopsis CRY1 and CRY2 mediated the blue light dependent inhibition of hypocotyl growth.And light cycle control of flowering.There is evidence that the Arabidopsis CRY dimerization is essential for the initiation of blue light signal transduction, but the relationship between the dimerization and photoexcitation is still unknown. To research on this topic, firstly established the expression of plant cryptochrome CRY2 using HEK293 T expression system, and the biological function of CRY2 were identified. Secondly, it was the first time that the CRY protein dimerization and oligomerization were directly observed. It was the basis for the next analysis of the process in the initiation of blue light signal transduction. Using a variety of redox agent, and an oxidizing agent further demonstrated that blue light formation of dimerization and oligomerization, was relied on cysteine mediated disulfide bonds. Further characterized of Arabidopsis CRY2 which one of eleven cysteines that play a role in this process.There are two unknown function protein BIC and BIC2 in Arabidopsis.BIC1 or overexpression phenotypes bic1 D and BIC2 got the same phenotype of cry1/cry2 double mutants. On this basis, firstly BICs could directly interact with CRY2, and showed strong blue light response. BICs could directly affect CRY2 blue light dependent dimerization and oligomerization. Further being proved by Co-IP experiment, BIC could affect CRY2-CRY2 interaction under blue light, and Split-luc experiments showed the same result.The following conclusions obtained by the above study: 1.the use of optimized HEK293T expression system expressed CRY2 could absorb blue light, and could play a normal biological function.2.The cysteine-mediated protein disulfide bonds under blue light,was the key step of CRY2 blue-light dependent formation of dimer and oligomer. And protein dimer and oligomer formation is dependent on the oxidation state of the micro-environment of the cells, a strong reducing agent could not form protein dimer and oligomer. Dimer and oligomer of CRY2C89 S, point mutation almost disappeared, Dimer and oligomer of CRY2C39 S,CRY2C158S, and CRY2C583 S, decreased. 3.BICs could be suppressed Cryptochrome related photomorphogenesis, and inhibit CRY2 phosphorylation and degradation. This suppression function was relied on the direct interaction with CRY2/BICs under blue light can inhibit the formation of CRY2 Dimer and oligomer to regulate plant growth and development.