Effect Of Ethylene And Light On Hypocotyl Elongation In Arabidopsis And Exploration Of Chorispora Bungeana Unknown Protein Functions

Ethylene and light act through specific signal transduction mechanisms to coordinate the development of higher plants. Application of1-aminocyclopropane-l-carboxylic acid （ACC, an ethylene precursor） suppresses the hypocotyl elongation of Arabidopsis seedlings in dark, but stimulates it in light. Ethylene can regulate auxin content, which has a great influence on plant development and morphology. However, the mechanisms of opposite effects of ethylene on hypocotyl elongation in light and dark remain unclear. In this study, we investigated the key factors involved in the opposite effects of ethylene on hypocotyl elongation in Arabidopsis seedlings. Results showed that the effects of ACC on hypocotyl elongation of1AA-insensitive mutants including tirl-1, axrl-3, and axrl-12seedlings were reduced in light but not in dark. The DR5promoter, a synthetic auxin-response promoter, is used to quantify the level of IAA responses. There was a marked increase in DR5-GFP signals in response to ACC treatment in hypocotyls of DR5-GFP seedlings in light but not in dark. COP1（CONSTITUTIVELY PHOTOMORPHOGENIC1） is a very important downstream component of light signaling. EIN3（ETHYLENE-INSENSITIVE3, an ethylene-stabilized transcription factor）, directly regulates ERF1（ETHYLENE-RESPONSE-FACTOR1）. The copl-4mutant treated with ACC and copl-4/EIN3ox plants have long hypocotyls in dark. Expression of ERF1in the copl-4mutant was induced by ACC treatment in dark, but the expression of ERF1in the wild-type was not affected. Taken together, ethylene promoting hypocotyl via IAA is mediated by light, and COP1has a significant impact on the transcription of some genes downstream of EIN3, and COP1plays a crucial role in opposite effects of ethylene on hypocotyl elongation.Chorispora bungeana is a kind of special cruciferous plant growing in the high altitude and high latitude region. It has a unique resistance mechanism to survive in the severe environments （big temperature difference between day and night, ultraviolet radiation intensity, etc）. Therefore, Chorispora bungeana is an ideal model plant to search and explore resistant protein, especially for cold resistant protein. In this study, we cloned full-length CDS sequences of four unknown proteins （Cb7660Ch Cb56880、Cb18740、Cb29780） from Chorispora bungeana. They have more than80%homology with the unknown protein corresponding to Arabidopsis thaliana （Atlg76600. At3g56880, Atlg18740and At4g29780） and could be induced by low temperature. So we used the corresponding unknown proteins （At1g18740） of Arabidopsis to further study the functions of Cb18740among these unknown proteins in Chorispora bungeana. It was predicted that At1g18740might be located in the nucleus and have a rod-like three dimensional structure. The N-terminal residues of At1g18740had a direct interaction with At5g52250. It has been indicated that At5g52250showed the directly interacted with CDPK11in the ABA signaling pathway although it is an unknown protein. Salk₀20993is a T-DNA insertion mutant of At1g18740. The characteristics of it are growing slowly, easy to aging and sensitive to vernalization promotion of germination, but more sensitive to ABA. The genes of ABA related were consistent in the responses to ABA both in salk₀20993and wild type. But ABA could induce great expression of ABI2in Salk₀20993. All related mutants of At1g18740were not sensitive to vernalization promotion of germination. Microarray analysis results showed that three genes （WRKY40ERF4and CYP707A3） were negatively regulated in Salk₀20993which were negative regulated ABA signaling pathway. To sum up, At1g18740maybe a negative regulated regulator component of ABA signaling pathway.