Abstract
Bax inhibitor-1 (BI-1) is an endoplasmic reticulum (ER)-resident cell death suppressor evolutionarily conserved in eukaryotes. The ability of BI-1 to inhibit the biotic and abiotic stresses have been well-studied in Arabidopsis, while the functions of wheat BI-1 are largely unknown. In this study, the wheat BI-1 gene TaBI-1.1 was isolated by an RNA-seq analysis of Fusarium graminearum (Fg)-treated wheat. TaBI-1.1 expression was induced by a salicylic acid (SA) treatment and down-regulated by an abscisic acid (ABA) treatment. Based on β-glucuronidase (GUS) staining, TaBI-1.1 was expressed in mature leaves and roots but not in the hypocotyl or young leaves. Constitutive expression of TaBI-1.1 in Arabidopsis enhanced its resistance to Pseudomonas syringae pv. Tomato (Pst) DC3000 infection and induced SA-related gene expression. Additionally, TaBI-1.1 transgenic Arabidopsis exhibited an alleviation of damage caused by high concentrations of SA and decreased the sensitivity to ABA. Consistent with the phenotype, the RNA-seq analysis of 35S::TaBI-1.1 and Col-0 plants showed that TaBI-1.1 was involved in biotic stresses. These results suggested that TaBI-1.1 positively regulates SA signals and plays important roles in the response to biotic stresses. In addition, TaBI-1.1 interacted with the aquaporin TaPIP1, and both them were localized to ER membrane. Furthermore, we demonstrated that TaPIP1 was up-regulated by SA treatment and TaPIP1 transgenic Arabidopsis enhanced the resistance to Pst DC3000 infection. Thus, the interaction between TaBI-1.1 and TaPIP1 on the ER membrane probably occurs in response to SA signals and defense response.
Highlights
Crop plants are constantly exposed to a variety of biotic and abiotic stresses, such as drought, salinity and pathogen infection, leading to major losses in productivity
Salicylic acid is a key signal in disease resistance, inducing local acquired resistance (LAR) and systemic acquired resistance (SAR), and leads to the increased expression of many defense proteins, including PR proteins
PR1 expression was slightly increased in the atbi1-2 mutant following treatment with Pst DC3000, and the extent of the increase of PR1 expression in atbi1-2 was significantly lower than that in Col-0 (Figure 2F)
Summary
Crop plants are constantly exposed to a variety of biotic and abiotic stresses, such as drought, salinity and pathogen infection, leading to major losses in productivity. The plant hormone salicylic acid (SA) plays an important role in the plant response to biotic stress. As a key signal in the plant defense response, SA induces broad-spectrum systemic resistance by up-regulating the expression of pathogenesis-related (PR) genes and promoting cell wall rigidification and phytoalexin synthesis (Ryals et al, 1996; Dong, 1998; Pieterse and van Loon, 1999; Wildermuth et al, 2001). The SA level is normally increased in tissues attacked by pathogens, which induces the expression of PR genes, including PR1, PR2, and PR5, to enhance plant resistance (Bari and Jones, 2008; Canet et al, 2012; Peng et al, 2012; Tateda et al, 2014; Choi et al, 2015). ISOCHORISMATE SYNTHASE 1 (ICS1) and DISEASE SUSCEPTIBILITY 1 (EDS1) play key roles in disease resistance. ICS1 encodes a key enzyme in SA biosynthesis (Wildermuth et al, 2001), whereas EDS1 controls basal immunity by restricting the growth of virulent pathogens (Wiermer et al, 2005)
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