Characterization Of Jacalin Gene Family And Calreticulin Gene Of Wheat

Scab disease, caused by Fusarium graminearum Schwabe, is a destructive disease of wheat worldwide, result in great yield losses and poor grain quality. So, isolation and characterization of the defense-related genes for scab would not only increase our understanding of the scab resistance mechanisms, but also enrich the candidate genes for fighting against the disastrous scab disease.To disentomb defense-related genes, we identified the jacalin-related lectin (JRL) gene response to various biotic and/or abiotic stresses. We identified53EST contigs and sigletons encoding JRL genes in wheat through mining the NCBI wheat EST database. Based on number of jacalin domain of wheat, rice and Arabidopsis, JRL genes can be classified into four groups. These JRL genes have diverse exon-intron structures. Although the overall pairwise protein sequence identity is modest and the overall architecture of JRLs proteins showed marked individual differences, the jacalin domain display highly conserved peculiarities. Microarray and MPSS data and real-time PCR revealed that JRL genes showed different tempo-spatial expression, suggesting that these genes may function at different stages of plant growth and development. Meanwhile, many JRL genes were response to various biotic and/or abiotic stress conditions and phytohormone applied, and the ratio of stress response JRL genes in every group altered gradually with the increasing of number of jacalin domain. Major stress-responsive OsJRL and At JRL genes contained putative corresponding stress-responsive cis-elements. These results showed that JRL genes had redundant but distinct functions.To research the disease resistance of JRL genes, we had identified a Triticum-specific jacalin-related lectin(TaJRL1) gene from scab-resistant wheat (Triticum aestivum L) cv. Wangshuibai. TaJRLl encodes a novel acidic polypeptide with two jacalin domains, and it was located mainly in the nuclei. Pathogen infection, phytohormone treatments, drought and heat shock stresses induced expression of TaJRLl; while application of the salicylic acid (SA) biosynthesis inhibitor paclobutrazol (PAC), or jasmonic acid (JA) biosynthesis inhibitor diethyldithiocarbamic acid (DIECA) substantially inhibited its expression. Attenuating TaJRLl through virus-induced gene silencing (VIGS) enhanced susceptibility to facultative fungal pathogen Fusarium graminearum and biotrophic fungal pathogen Blumeria graminis. Arabidopsis plants transformed with TaJRLl displayed increased resistance to Fusarium graminearum and Botrytis cinerea. The JA and SA levels in these transgenic Arabidopsis thaliana plants rose significantly. The loss or increase of disease resistances because of alternation of TaJRL1function correlated well with attenuation or enhancement of the SA-and JA-dependent defense signaling pathways. These results suggested that TaJRLl appears to have a role in feedback amplification of the defense signaling pathways.Similaring to JRL, calreticulin (CRT) is also a kind of plant lectins. In this study, we characterized three CRT gene family memers from wheat cv. Wangshuibai. Phylogenetic analysis showed that CRT proteins were well conserved among monocots and dicots, and were grouped into CRT1/2and CRT3subfamilies. Their transcripts were mainly detected in reproductive tissues, and TaCRTl/3were also highly expressed in vegetative tissues. Fusarium grminearum infection and elicitor DON treatment induced TaCRT genes expression. TaCRT1was up-regulated by JA treatment, TaCRT2was induced by JA and ETH treatments, TaCRT3was up-regulated by SA and JA treatment. Overexpression of TaCRTl in Arabidopsis decreased resistance to Botrytis cinerea, however, dsTaCRTl transgenic Arabidopsis thaliana enhanced resistance. Immunogold localization showed that TaCRT1and dsTaCRTl targeted to ER and cytoplasmic, and cytoplasmic, respectively. qRT-PCR showed that calcium-binding protein gene (CBP60g) and genes (PAD4, ICS1, EDS5, PR1and PR2) in SA-dependent defense signaling pathway were up-regulated in dsTaCRTl transgenic plants. These genes were down-regulated in TaCRTl transgenic plants. Our results indicated that TaCRT1might regulate SA-mediated defense signaling pathway by CBP60g gene.