Research Of Temperature Related Mutant Lls1(Long Life Span 1) In Arabidopsis And Its Mutant Gene

Plant growth and development is a very complicated process, affected by a variety of external environment factors (such as temperature, light) and inner factors (such as endogenous phytohormones). In order to maintain the balance of plant growth and development, there is a complete set of regulatory mechanism. The temperature is one of the important factors involved in the regulation of plant growth and development. However, the information of the mechanism and temperature signal transduction is far less clear. Arabidopsis mutant lls1 (Long Life Span 1) is sensitive to temperature and its phenotype will loose under high temperature. So the research on this mutant and its mutant gene will help to reveal the temperature regulation mechanism of plant growth and development. This study focuses on the analysis of the mutant lls1 mutation phenotype, the determination of mutated genes and functional analysis. And the main research contents and results are as followed:1. The mutant lls1 showed the phenotypic characteristics under low temperature conditions. Low temperature affects the growth of root and leaf in Arabidopsis, the growth of mutant lls1 root length and leaf is slow at room temperature, it showed the phenotype of wild type under low temperature, these phenotype is consistent with that of the mutant, the slow growth, small leaf, extremely dwarf and so on; While it is not completely consistent with that, svp mutant's flowering time is not sensitive to low temperature. In low temperatures, the leaf growth of svpl mutant was not affected by low temperature obviously. The expression of SVP gene, flowering suppressor FLM, TFL, and low temperature response gene KIN2, COR15A increased in the low temperature. This might be the reason that low temperature inhibits plant growth and flowering was delay; While the expression of flower suppressor gene FLM, TFL, SVP had no obvious change under the low temperature treatment in mutant lls1, and the temperature response gene KIN2, COR15A also had weak expression. It was speculated that the mutations gene lls1 might interrupt some cryogenic response link so that the response of these gene could not be induced.2. llsl mutation phenotype was caused by KAN3 and GAAP1 mutation. Since the T-DNA insert in both GAAP1 and KAN3 gene, the relationship between some mutant phenotypes of lls1 and the two genes was analyzed. It was found that kan3 mutant was similar with lls1 in silique length, GUS staining and in situ hybridization analysis found that KAN3 gene expressed strongly in anthesis at particular stage of pollen development, and weakly in young embryo; And GAAP1 expressed in pollen and pistil during early flower development stage; Further physiology analysis found that gaapl mutants and lls1 mutants showed similar responses to sugar, both mutants were less sensitive to sugar signal. While in cytokinins response, kan3 mutant was very similar with llsl mutant. Additionally, some lls1 phenotype such as hairy leaves and more branches were found in F1 population of double mutant kan3gaap. So we speculated that the temperature sensitive mutant lls1 is caused by the GAAP1 and KAN3 gene mutations. And gene mutations change the sensitivty of cytokinins and sugar signal response, resulting in smaller cells, the emergence of plant dwarf, loss of apical dominance and other characteristics during the process of development.3. GAAP1 improve the plants resistance to abiotic stress through ABA and UPR pathway. Overexpression plant GAAP1-OX, wild type Col, and gaapl mutant were treated with ER stress factor TM, GAAP1-OX was the least affected by TM, gaapl was injuried most seriously, reactive oxygen species generated most; Also gaapl's root was inhibited by ABA seriously, Q-RT esults showed that gaapl mutations enhanced ABA signal transduction genes ABI1, ABI2, stress response genes RD29A and RAB18, reactive oxygen species induced genes AtGSTUS and APX1, It suggested that GAAP1 gene may be involved in ABA mediated stress response; UPR gene expression analysis showed that mutation of GAAP1 reduced the expression of UPR gene induced by ER-stress, It indicated that GAAP1 was involved in the regulation of UPR pathway to suppress the programmed cell death.To sum up, the temperature sensitivity mutants llsl was caused by KAN3 and GAAPl gene mutation, at room temperature, the mutant lls1 show the phenotype of that of wild type under low temperature, the mutant changed some gene expression response under the low temperature; GAAPl improved the plants resistance to abiotic stress might through ABA and UPR pathway. The further study of KAN3 and GAAPl function will help to clarify the temperature sensitivity mechanism in mutant llsl, promote the understanding of plant growth and resistance mechanism.