Zhengning Jiang

Transformation of Wheat Thaumatin-Like Protein Gene and Analysis of Reactions to Powdery Mildew and Fusarium Head Blight in Transgenic Plants

Abstract A thaumatin-like protein gene, Ta-Tlp , was cloned from wheat in previous studies, which was expressed in a high level in wheat ( Triticum aestivum L.) 6VS/6AL translocation line with high resistance to powdery mildew ( Erysiphe graminis f.sp. tritici Em. Marchal.), implying its close relation to the resistance of the disease. To further understand the genes function, Ta-Tlp was constructed into an expression vector driven by the strong ubi promoter. The vector pAHC-TlP constructed was transformed into immature embryo-derived calli of common wheat cultivar Yangmai 158 through particle bombardment. After two rounds of herbicide bialaphos selection and regeneration, herbicide-resistance plants were obtained. The Ta-Tlp proved to be integrated into the wheat genome and was expressed in T 1 and T 2 generations by PCR, Southern blot, and RT-PCR analysis. The transgenic plants of T 0 , T 1 , and T 2 generations were inoculated by E. graminis and Fusarium graminearum for resistance identification. All plants of T 0 , T 1 , and T 2 generations were resistant to wheat powdery mildew by delaying disease development, but no distinct resistance to Fusarium head blight.

RLP1.1, a novel wheat receptor-like protein gene, is involved in the defence response against Puccinia striiformis f. sp. tritici

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most serious diseases of wheat; therefore, exploring effective resistance-related genes is critical for breeding and studying resistance mechanisms. However, only a few stripe rust resistance genes and defence-related genes have been cloned. Moreover, transgenic wheat with enhanced stripe rust resistance has rarely been reported. Receptor-like proteins (RLPs) are known to be involved in defence and developmental pathways. In this research, a novel RLP gene TaRLP1.1 was characterized as an important stripe rust defence gene. TaRLP1.1 was screened by GeneChip and was found to be induced by Pst specifically in the resistant variety. Knock down of TaRLP1.1 in the stripe rust-resistant plants resulted in increased susceptibility to Pst, and phenolic autofluorogen accumulation at the pathogen–host interaction sites, usually correlated with the hypersensitive response, was decreased dramatically. However, when the TaRLP1.1 gene was transformed into the susceptible wheat variety Yangmai158, the transgenic plants showed highly increased resistance to Pst, and the hypersensitive response was enhanced at the infection sites. Meanwhile, the expression of pathogenesis-related genes decreased in the TaRLP1.1-silenced plants and increased in the TaRLP1.1-overexpressing plants. Thus, it was proposed that TaRLP1.1 greatly contributed to the hypersensitive response during the pathogen–host interaction. Along with the functional analysis, an evolutionary study of the TaRLP1 family was performed. Characterization of TaRLP1.1 may facilitate breeding for stripe rust resistance and better understanding of the evolution of the RLP genes in wheat.

The Hv-SGT1 Gene from Haynaldia villosa Contributes to Resistances Towards Both Biotrophic and Hemi-Biotrophic Pathogens in Common Wheat (Triticum aestivum L.)

The SGT1 protein is essential for R protein-mediated and PAMPs-triggered resistance in many plant species. Here we reported the isolation and characterization of the Hv-SGT1 gene from Haynaldia villosa (2n = 14, VV). Analysis of the subcellular location of Hv-SGT1 by transient expression of a fusion to GFP indicated its presence in the cytoplasm and nucleus. Levels of Hv-SGT1 transcripts were increased by inoculation with either the biotrophic pathogen Blumeria graminis DC. f. Sp. tritici (Bgt) or the hemi-biotrophic pathogen Fusarium graminearum (Fg). Levels of Hv-SGT1 showed substantial increase following treatment with H2O2 and methyl jasmonate (MeJA), only slightly induced following exposure to ethephon or abscisic acid, but not changed following exposure to salicylic acid. The demonstration that silencing of Hv-SGT1 substantially reduced resistance to Bgt indicated that Hv-SGT1 was an essential component of disease resistance in H . villosa . The over-expression of Hv-SGT1 in Yangmai 158 enhanced resistance to powdery mildew, and this correlated with increased levels of whole-cell reactive oxygen intermediates at the sites of penetration by the pathogens. Compared with wild-type plants, the expression levels of genes related to the H2O2 and JA signaling pathways were lower in the Hv-SGT1 silenced plants and higher in the Hv-SGT1 over-expressing plants. Therefore, the involvement of Hv-SGT1 in H2O2 production correlates with the hypersensitive response and jasmonic acid signaling. Our novel demonstration that wheat with over-expressed Hv-SGT1 showed enhanced resistance to both powdery mildew and FHB suggests that it could served as a transgenic genetic resource in wheat breeding for multiple disease resistance.

Efficient marker-assisted screening of structural changes involving Haynaldia villosa chromosome 6V using a double-distal-marker strategy

Abstract Wild relatives of wheat possess many agronomic traits important to wheat improvement. Wheat–alien translocation and deletion lines are important genetic stocks in wheat breeding or physical mapping of important alien genes. However, screening for chromosomal structural changes by conventional cytogenetic analyses is time-consuming work. It is necessary to develop an efficient method of finding alien chromosomal structural changes. In this research, two amplicon markers, 6VS-381 and 6VL-358, specific to the distal regions of the short and long arms, respectively, of Haynaldia villosa chromosome 6V, were developed based on the expressed sequence tags located on the distal regions of wheat group 6. Marker-assisted screening work was then carried out in two individual radiation-induced populations. The first contained 365 plants involving 43 M1:2 families derived from a pollen irradiation treatment of a wheat–H. villosa monosomic 6V addition line. The other was a M1 population containing 100 plants derived from an irradiation treatment of a wheat–H. villosa disomic 6V(6A) substitution line. The female parent in both treatments was a common wheat cultivar Chinese Spring. Those plants marked by a single positive distal marker were considered to be putative structural changes of 6V. After cytogenetic analysis, a total of 20 structure-changed chromosomes were identified, comprising 12 whole-arm translocations, four terminal translocations, one 6VL terminal deletion, one translocation deletion, and two intercalary translocations. The double-distal-marker strategy proposed in this study gives an efficient model for finding structural aberrations involving a specific alien chromosome.

Pm21, Encoding a Typical CC-NBS-LRR Protein, Confers Broad-Spectrum Resistance to Wheat Powdery Mildew Disease

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Map-based cloning of the gene Pm21 that confers broad spectrum resistance to wheat powdery mildew

Common wheat (Triticum aestivum L.) is one of the most important cereal crops. Wheat powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a continuing threat to wheat production. The Pm21 gene, originating from Dasypyrum villosum, confers high resistance to all known Bgt races and has been widely applied in wheat breeding in China. In this research, we identify Pm21 as a typical coiled-coil, nucleotide-binding site, leucine-rich repeat gene by an integrated strategy of resistance gene analog (RGA)-based cloning via comparative genomics, physical and genetic mapping, BSMV-induced gene silencing (BSMV-VIGS), large-scale mutagenesis and genetic transformation.

Genetic Analysis of Fusarium Head Blight Resistance in CIMMYT Bread Wheat Line C615 Using Traditional and Conditional QTL Mapping

Fusarium head blight (FHB) is a destructive wheat disease present throughout the world, and host resistance is an effective and economical strategy used to control FHB. Lack of adequate resistance resource is still a main bottleneck for FHB genetics and wheat breeding research. The synthetic-derived bread wheat line C615, which does not carry the Fhb1 gene, is a promising source of FHB resistance for breeding. A population of 198 recombinant inbred lines (RILs) produced by crossing C615 with the susceptible cultivar Yangmai 13 was evaluated for FHB response using point and spray inoculations. As the disease phenotype is frequently complicated by other agronomic traits, we used both traditional and multivariate conditional QTL mapping approaches to investigate the genetic relationships (at the individual QTL level) between FHB resistance and plant height (PH), spike compactness (SC), and days to flowering (FD). A linkage map was constructed from 3,901 polymorphic SNP markers, which covered 2,549.2 cM. Traditional and conditional QTL mapping analyses found 13 and 22 QTL for FHB, respectively; 10 were identified by both methods. Among these 10, three QTL from C615 were detected in multiple years; these QTL were located on chromosomes 2AL, 2DS, and 2DL. Conditional QTL mapping analysis indicated that, at the QTL level, SC strongly influenced FHB in point inoculation; whereas PH and SC contributed more to FHB than did FD in spray inoculation. The three stable QTL (QFhbs-jaas.2AL, QFhbp-jaas.2DS, and QFhbp-jaas.2DL) for FHB were partly affected by or were independent of the three agronomic traits. The QTL detected in this study improve our understanding of the genetic relationships between FHB response and related traits at the QTL level and provide useful information for marker-assisted selection for the improvement of FHB resistance in breeding.

Quantitative trait loci responsible for sharp eyespot resistance in common wheat CI12633

Sharp eyespot is a major fungal disease of wheat caused by Rhizoctonia cerealis in cool and humid environments worldwide. In this study, 224 single seed descent derived F13, F14 and F15 recombinant inbred lines (RILs) from the cross between CI12633 (a resistant cultivar) and Yangmai 9 (a susceptible cultivar) were assessed for sharp eyespot resistance (R.cerealis isolate R0301) in field and greenhouse conditions in three growing seasons. Different agronomic characteristics were also evaluated in the field with no disease infection. All the lines were genotyped with the Illumina iSelect 90 K SNP wheat chip and 101 SSR markers. Sharp eyespot resistance was significantly negatively correlated with heading date and tiller angle, and significantly positively correlated with the diameter of the basal first internode and second internode. Five QTL with a likelihood of odds ratio score of higher than 3.0 were detected on chromosomes 2BS, 4BS, 5AL and 5BS, respectively. These identified QTL may be used in future wheat breeding programs through marker assisted selection for developing sharp eyespot resistant cultivars.