| Transcriptional regulation is an important mechanism for plants response to pathogens and insects. The process could be activated by infection of pathogens, attack of insects or treatments by biotic or abiotic stimuli. Arabidopsis transcription factor AtMYB44was induced by exogenous application of harpin, an effector from rice pathogen Xanthomonas oryzae. AtMYB44regulate insect resistance and pathogen resistance by activating the ethylene signal pathway and salicylic acid signal pathway respectively. As the important role of transcriptional regulation and few related studies conducted on wheat, a computational pipeline was designed for identification of MYB transcription factors based on wheat ESTs database. Meanwhile, an ABA-induced MYB3R gene was isolated from Triticum aestivum L, and its functions were studied in detail. Experiments confirmed its roles in wheat against abiotic stress. Moreover, in previous work, a fragment of harpin (an effector from Xanthomonas oryzae) was confirmed to have many beneficial phenotypes on plants by exogenous application. The fragment was chosen as transgene, constructed for wheat transformation vector and delivered into Yangmai16cultivar by bombardment. After selection and PCR detection, the transgene was confirmed to integrate into wheat genome.1. Large-scale in silico identification of MYB family genes from wheat expressedsequence tagsThe MYB proteins constitute one of the largest transcription factor families in plants and much has been done about their structures, functions and evolution especially in model plants Arabidopsis and rice. However, wheat as a major crop, with no available genome sequence information yet, is less studied in this transcription factor family. Despite that, expressed sequence tags (ESTs) as an important resource, provided us an opportunity for large scale gene identification. In this study, a total of218sequences were identified and confirmed as putative MYB proteins consisting of MYB1R, R2R3-type MYB, MYB3R and MYB4R types. Thirty-six R2R3-type MYB genes with complete open reading frames (ORFs) were obtained. The putative orthologs in rice and Arabidopsis were assigned based on the phylogenetic tree. Tissue specific expression patterns analysis confirmed the realibility of orthologs’ prediction and could transfer the gene information from Arabidopsis to wheat. Moreover, the motifs flanking the MYB domain were analyzed by MEME web server. The distribution of motifs among wheat MYB proteins was described and this could facilitate the subfamily classification.2. Cloning and functional analysis of TaMYB3Rl gene in wheat(Triticum aestivum L.)Abiotic stress seriously affects crop growth and productivity. To better understand the mechanisms plants use to cope with drought, cold and salt stress, it is necessary to isolate and characterize important regulators response to these stresses. In this study, a novel MYB3R gene was isolated from wheat (Triticum aestivum L.)and designated as TaMYB3R1based on its conserved three repeats in MYB domain. The sequence of TaMYB3R1protein shares high degree of identity to other plant MYB3R proteins. Subcellular localization experiment in onion epidermal cells proved that TaMYB3Rl localized in the nucleus. Trans-activation essays in yeast cells confirmed that TaMYB3R1was a transcriptional activator, and only C-terminal region was able to activate the expression of β-galactosidase. The expression of TaMYB3Rl was induced by exogenous applications of phytohormone ABA and MeJA treatment and also under abiotic stress. In addition, TaMYB3R1-overexpressed Arabidopsis were more tolerance to drought and salt stresses. Moreover, TaMYB3R1influenced expression of both ABA-dependent and ABA-independent responsive genes, implicating TaMYB3R1in diverse osmotic stress-response mechanisms in Arabidopsis.3. Generation of Hpal10.42transgenic wheat and test of resistance to FHB and aphidsThe production and quality of wheat is seriously affected by pest wheat-aphids and pathogen Fusarium graminearum, both of which are worldwide threat and hard to control. It is difficult to obtain the resistant cultivars to aphids or F. graminearum by traditional breeding because of limited resistant sources. With the development of plant genetic engineering techniques,we can use a variety of sources besides plants and integrated them into plants,produced transgenic plants with high quality, production and resistance.Our previous studies indicated that effector harpins could elicit different plant growth and defense signal pathways by exponent application, thereafter cause many beneficial phenotypes of plants, including promoting growth, tolerance to drought and also resistance to pests and pathogens. In present study, we constructed wheat transformation vector by using a fragment of harpins Hpal10-42as the transgene, then delivered it into wheat cultivar Yangmail6by bombardment. After selection and reproduction, we successfully obtained T1transgenic plants. We next recorded the phenotypes including height and number of tillers, and tested resistance to aphids and F. graminearum. The results showed that compared to wild plants, transgenic plants had less symptoms and the pathogen developed more slowly after inoculation with F. graminearum; as to aphids, transgenic plants had less number of aphids colonized, this gave hinds that the resistance is acquired by prohibiting the colonization. |
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