GhTBL34 Is Associated with Verticillium Wilt Resistance in Cotton

Verticillium wilt (VW) is a typical fungal disease affecting the yield and quality of cotton. The Trichome Birefringence-Like protein (TBL) is an acetyltransferase involved in the acetylation process of cell wall polysaccharides. Up to now, there are no reports on whether the TBL gene is related to disease resistance in cotton. In this study, we cloned a cotton TBL34 gene located in the confidence interval of a major VW resistance quantitative trait loci and demonstrated its relationship with VW resistance in cotton. Analyzing the sequence variations in resistant and susceptible accessions detected two elite alleles GhTBL34-2 and GhTBL34-3, mainly presented in resistant cotton lines whose disease index was significantly lower than that of susceptible lines carrying the allele GhTBL34-1. Comparing the TBL34 protein sequences showed that two amino acid differences in the TBL (PMR5N) domain changed the susceptible allele GhTBL34-1 into the resistant allele GhTBL34-2 (GhTBL34-3). Expression analysis showed that the TBL34 was obviously up-regulated by infection of Verticillium dahliae and exogenous treatment of ethylene (ET), and salicylic acid (SA) and jasmonate (JA) in cotton. VIGS experiments demonstrated that silencing of TBL34 reduced VW resistance in cotton. We deduced that the TBL34 gene mediating acetylation of cell wall polysaccharides might be involved in the regulation of resistance to VW in cotton.     

Hormonal Responses to Susceptible,Intermediate, and Resistant Interactions in the Brassica napus–Leptosphaeria maculans Pathosystem

Hormone signaling plays a pivotal role in plant–microbe interactions. There are three major phytohormones in plant defense: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The activation and trade-off of signaling between these three hormones likely determines the strength of plant defense in response to pathogens. Here, we describe the allocation of hormonal signaling in Brassica napus against the fungal pathogen Leptosphaeria maculans. Three B. napus genotypes (Westar, Surpass400, and 01-23-2-1) were inoculated with two L. maculans isolates (H75 8-1 and H77 7-2), subsequently exhibiting three levels of resistance: susceptible, intermediate, and resistant. Quantitative analyses suggest that the early activation of some SA-responsive genes, including WRKY70 and NPR1, contribute to an effective defense against L. maculans. The co-expression among factors responding to SA/ET/JA was also observed in the late stage of infection. The results of conjugated SA measurement also support that early SA activation plays a crucial role in durable resistance. Our results demonstrate the relationship between the onset patterns of certain hormone regulators and the effectiveness of the defense of B. napus against L. maculans.     

Genetic Variations of TAP1 Gene Exon 3 Affects Gene Expression and Escherichia coli F18 Resistance in Piglets

Firstly, our research group identified Sutai pigs’ phenotypes that exhibited extreme resistance and susceptibility to the Escherichia coli F18 respectively, and then eight ETEC (Enterotoxigenic Escherichia coli) F18-resistant piglets and eight ETEC F18-sensitive piglets were selected. Then, the TAP1 (Transporter associated with antigen processing) mRNA relative expression levels were analyzed in 11 tissues of the resistant and susceptible phenotypes. Simultaneously, we detected the genetic variations in exon 3 of the TAP1 gene and evaluated the TAP1 mRNA expression levels among the different genotype pigs to study the effects of the genetic variation on gene expression, and the E. coli F18 resistance. The results revealed higher expression levels in the resistant genotypes than that in the susceptible genotypes in 11 tissues, with significant differences in the spleen, lymph node, lung, thymus, duodenum and jejunum. Furthermore, a G729A mutation was identified in the TAP1 gene exon 3, and this mutation deviates from Hardy-Weinberg equilibrium (p < 0.01). The TAP1 mRNA levels in GG genotype were significantly higher than that in the other two genotypes, with significant differences in the liver, lung, kidney, thymus, lymph node, duodenum and jejunum tissues. We speculated that high expression of the TAP1 gene might confer resistance against the E. coli F18, the G729A mutation had a significant effect on the mRNA expression, and individuals with the GG genotype possessed a stronger ability to resist the E. coli F18 infection.     

Quantitative Trait Loci Mapping for Bacterial Blight Resistance in Rice Using Bulked Segregant Analysis

Oryza meyeriana is highly resistant to rice bacterial blight (BB) and this resistance trait has been transferred to cultivated rice (O. sativa) using asymmetric somatic hybridization. However, no resistance genes have yet been cloned. In the present study, a progeny of the somatic hybridization with high BB resistance was crossed with a rice cultivar with high BB susceptibility to develop an F₂ population. Using bulked segregant analysis (BSA), 17 polymorphic markers that were linked to rice BB resistance were obtained through scanning a total of 186 simple sequence repeats (SSR) and sequence-tagged site (STS) markers, evenly distributed on 12 chromosomes. A genetic linkage map was then constructed based on the 17 linkage markers and the F₂ segregating population, which was followed by mapping for quantitative trait loci (QTLs) for BB resistance. Three QTLs were identified on chromosomes 1, 3 and 5, respectively, and the alleles of the resistant parent at any of the QTLs increased BB resistance. All of the three QTLs had a strong effect on resistance, explaining about 21.5%, 12.3% and 39.2% of the resistance variance, respectively. These QTLs were different from the loci of the BB resistance genes that have been identified in previous studies. The QTLs mapped in this work will facilitate the isolation of novel BB resistance genes and their utilization in rice resistance breeding.     

Identification and Expression Analysis of Candidate Genes Associated with Defense Responses to Phytophthora capsici in Pepper Line “PI 201234”

Phytophthora capsici (Leonian), classified as an oomycete, seriously threatens the production of pepper (Capsicum annuum). Current understanding of the defense responses in pepper to P. capsici is limited. In this study, RNA-sequencing analysis was utilized to identify differentially expressed genes in the resistant line “PI 201234”, with 1220 differentially expressed genes detected. Of those genes, 480 were up-regulated and 740 were down-regulated, with 211 candidate genes found to be involved in defense responses based on the gene annotations. Furthermore, the expression patterns of 12 candidate genes were further validated via quantitative real-time PCR (qPCR). These genes were found to be significantly up-regulated at different time points post-inoculation (6 hpi, 24 hpi, and 5 dpi) in the resistant line “PI 201234” and susceptible line “Qiemen”. Seven genes were found to be involved in cell wall modification, phytoalexin biosynthesis, symptom development, and phytohormone signaling pathways, thus possibly playing important roles in combating exogenous pathogens. The genes identified herein will provide a basis for further gene cloning and functional verification studies and will aid in an understanding of the regulatory mechanism of pepper resistance to P. capsici.     

Mass Spectrometry Based Metabolomics to Identify Potential Biomarkers for Resistance in Barley against Fusarium Head Blight (<Emphasis Type="Italic">Fusarium graminearum</Emphasis>)

Resistance in Triticeae to fusarium head blight (FHB) is quantitatively inherited. Metabolomics as a tool was used to better understand the mechanisms of resistance and to identify potential FHB resistance biomarker metabolites in barley. Five FHB-resistant two-row barley genotypes (CIho 4196, Zhedar-1, Zhedar-2, Fredrickson, and Harbin-2r) and one FHB-susceptible genotype (CH 9520–30) were each inoculated with either pathogen-suspension or mock-solution. Disease severity, quantified as the proportion of spikelets diseased, varied among genotypes, being the greatest in CH 9520–30. Spikelets were sampled, metabolites extracted with aqueous methanol, and analyzed using an LC-ESI-LTQ-Orbitrap system. A pair wise, resistant vs. susceptible, t-test identified 1774 significant treatment peaks. Canonical discriminant analysis of peak abundance allowed the genotypes to be sorted into three clusters: (i) CH9520-30, (ii) Harbin-2r, (iii) the remaining four genotypes. The t-test was further used to identify resistance-related (RR) and pathogenesis-related (PR) metabolites. The pathogen-produced virulence factor deoxynivalenol (DON), and its detoxification product, DON-3-O-glucoside (D3G) were designated as resistance indicator (RI) metabolites. Metabolites (RR, PR, or RI) occurring in at least two resistant genotypes, showing a two-fold or greater abundance in resistant vs. susceptible lines, and also known to have plant defense functions were selected as potential FHB resistance biomarker metabolites. These included phenylalanine, p-coumaric acid, jasmonate, linolenic acid, total DON produced (TDP), and the proportion of DON converted to D3G (PDC). Total DON was the lowest in CIho 4196, while PDC was the highest in Zhedar-2. The application of RR, PR, and RI metabolites as potential biomarkers to enhance resistance is discussed.     

Ascorbate–Glutathione Oxidant Scavengers,Metabolome Analysis and Adaptation Mechanisms of Ion Exclusion in Sorghum under Salt Stress

Salt stress is one of the major significant restrictions that hamper plant development and agriculture ecosystems worldwide. Novel climate-adapted cultivars and stress tolerance-enhancing molecules are increasingly appreciated to mitigate the detrimental impacts of adverse stressful conditions. Sorghum is a valuable source of food and a potential model for exploring and understanding salt stress dynamics in cereals and for gaining a better understanding of their physiological pathways. Herein, we evaluate the antioxidant scavengers, photosynthetic regulation, and molecular mechanism of ion exclusion transporters in sorghum genotypes under saline conditions. A pot experiment was conducted in two sorghum genotypes viz. SSG 59-3 and PC-5 in a climate-controlled greenhouse under different salt concentrations (60, 80, 100, and 120 mM NaCl). Salinity drastically affected the photosynthetic machinery by reducing the accumulation of chlorophyll pigments and carotenoids. SSG 59-3 alleviated the adverse effects of salinity by suppressing oxidative stress (H₂O₂) and stimulating enzymatic and non-enzymatic antioxidant activities (SOD, APX, CAT, POD, GR, GST, DHAR, MDHAR, GSH, ASC, proline, GB), as well as protecting cell membrane integrity (MDA, electrolyte leakage). Salinity also influenced Na⁺ ion efflux and maintained a lower cytosolic Na⁺/K⁺ ratio via the concomitant upregulation of SbSOS1, SbSOS2, and SbNHX-2 and SbV-Ppase-II ion transporter genes in sorghum genotypes. Overall, these results suggest that Na⁺ ions were retained and detoxified, and less stress impact was observed in mature and younger leaves. Based on the above, we deciphered that SSG 59-3 performed better by retaining higher plant water status, photosynthetic assimilates and antioxidant potential, and the upregulation of ion transporter genes and may be utilized in the development of resistant sorghum lines in saline regions.     

Glutathione Transferases Superfamily: Cold-Inducible Expression of Distinct GST Genes in Brassica oleracea

Plants, as sessile organisms, can suffer serious growth and developmental consequences under cold stress conditions. Glutathione transferases (GSTs, EC 2.5.1.18) are ubiquitous and multifunctional conjugating proteins, which play a major role in stress responses by preventing oxidative damage by reactive oxygen species (ROS). Currently, understanding of their function(s) during different biochemical and signaling pathways under cold stress condition remain unclear. In this study, using combined computational strategy, we identified 65 Brassica oleracea glutathione transferases (BoGST) and characterized them based on evolutionary analysis into 11 classes. Inter-species and intra-species duplication was evident between BoGSTs and Arabidopsis GSTs. Based on localization analyses, we propose possible pathways in which GST genes are involved during cold stress. Further, expression analysis of the predicted putative functions for GST genes were investigated in two cold contrasting genotypes (cold tolerance and susceptible) under cold condition, most of these genes were highly expressed at 6 h and 1 h in the cold tolerant (CT) and cold susceptible (CS) lines, respectively. Overall, BoGSTU19, BoGSTU24, BoGSTF10 are candidate genes highly expressed in B. oleracea. Further investigation of GST superfamily in B. oleracea will aid in understanding complex mechanism underlying cold tolerance in plants.