Molecular Cloning Of Jasmonate Induced Genes And Characterization Of Their Expression In Wheat

Jasmonic acid (JA) and its methyl ester (MeJA) collectively named jasmonates, are linoleic acid-derived cyclopeantanone-based compounds of wide distribution in the plant kingdom. They play important roles in plant growth and development as well as in plant defense. To further understand the biosynthesis and function of JA, a gene encoding a key enzyme involved in JA biosynthesis, effect of JA on response to low temperature in wheat and flowering time in Arabidopsis were focused on the thesis.A JA-induced cDNA library was constructed. The titer of the primary library was about 3-4 x 10 pfu/ml, and an average length of the insert was about 1.2 kb. TaJIP was a JA induced gene in wheat. The northern analysis indicated that it could also response to low temperature. It suggested that JA signal pathway was involved in the process of plant resistance to low temperature.When Arabidopsis was treated with exogenous JA, the flowering time was delayed not only in C24 ecotype but also in Col ecotype under the conditions of vernalization or non-vernalization. Delayed flowering was correlated to increasing expression of FLC, while CO was stable expression, It suggested that JA may play a role on delaying flowering through FLC in Arabidopsis.Allene oxide synthase (AOS) is the first enzyme in the lipoxygenase pathway which leads to the formation of JA. A full-length cDNA of TaAOS was cloned from winter wheat (Triticum aestivum L. cv. Jinghua NO.3) seedling. The open reading frame (ORF) consists of 1,410 bp encoding a polypeptide of 470 amino acids withcalculated molecular mass of 51.9 kDa and pI 9.39. Southern blot analysis suggested the gene exists with three copies in wheat genome. The TaAOS mRNA could be strongly induced by exogenous JA, and the highest level induced by JA was observed under treatment often hours. RNA in situ hybridization of seedling indicated the gene preferential expressed in young leaves, especially in the parenchyma cells around the vascular bundles, and in cells around vascular bundles in coleoptile and shoot apex. The hybridization also showed that exogenous La3+ could not reduce the expression of TaAOS induced by JA.