The pepper Bs4C proteins are localized to the endoplasmic reticulum (ER) membrane and confer disease resistance to bacterial blight in transgenic rice

Abstract

Transcription activator-like effector (TALE)-dependent dominant disease resistance (R) genes in plants, also referred to as executor R genes, are induced on infection by phytopathogenic bacteria of the genus Xanthomonas harbouring the corresponding TALE genes. Unlike the traditional R proteins, the executor R proteins do not determine the resistance specificity and may function broadly in different plant species. The executor R gene Bs4C-R in the resistant genotype PI 235047 of the pepper species Capsicum pubescens (CpBs4C-R) confers disease resistance to Xanthomonas campestris pv. vesicatoria (Xcv) harbouring the TALE genes avrBsP/avrBs4. In this study, the synthetic genes of CpBs4C-R and two other Bs4C-like genes, the susceptible allele in the genotype PI585270 of C. pubescens (CpBs4C-S) and the CaBs4C-R homologue gene in the cultivar 'CM334' of Capsicum annum (CaBs4C), were characterized in tobacco (Nicotiana benthamiana) and rice (Oryza sativa). The Bs4C genes induced cell death in N. benthamiana. The functional Bs4C-eCFP fusion proteins were localized to the endoplasmic reticulum (ER) membrane in the leaf epidermal cells of N. benthamiana. The Xa10 promoter-Bs4C fusion genes in transgenic rice conferred strain-specific disease resistance to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight in rice, and were specifically induced by the Xa10-incompatible Xoo strain PXO99 (pHM1avrXa10). The results indicate that the Bs4C proteins from pepper species function broadly in rice and the Bs4C protein-mediated cell death from the ER is conserved between dicotyledonous and monocotyledonous plants, which can be utilized to engineer novel and enhanced disease resistance in heterologous plants.

Transcriptome analysis reveals defense-related genes and pathways against Xanthomonas campestris pv. vesicatoria in pepper (Capsicum annuum L.)

“…Also, bs5 has been mapped and its linked markers are available [18]. These five dominant loci (Bs1-Bs4, Bs7) have been shown to confer resistance to Xcv in a gene-forgene manner [5,7,[13][14][15][16][17]19]. The executor R gene Bs1 in the resistant genotype VI037601 of the pepper species Capsicum annum L. confers disease resistance to Xcv strain 23-1 harbouring the avirulence gene avrBs1 [7].…”

“…Until now, five non-allelic dominant hypersensitive resistance genes, Bs1 - Bs4 , Bs7 and two recessive non-hypersensitive resistance genes, bs5 and bs6 , have been used in pepper [ 7 , 12 , 13 ]. While Bs2 , Bs3 , Bs4 and Bs7 have been cloned, for their molecular markers for marker-assisted selection (MAS) were developed [ 5 , 14 – 17 ]. Also, bs5 has been mapped and its linked markers are available [ 18 ].…”

Genetic modification to improve disease resistance in crops

“…For bacterial pathogens expressing transcription activator-like (TAL) effectors that activate the expression of susceptibility genes in the host, resistance can be engineered by deletion of the TAL DNA binding sites in the promoter (Li et al, 2012;Jia et al, 2017). Another approach to engineer resistance to these bacterial pathogens is to add TAL effector binding sites to a cell-death-promoting ('executor') gene that is triggered by the TAL effectors present in common pathotypes (Hummel et al, 2012;Wang et al, 2018a).…”

Transcriptome analysis of resistant and susceptible pepper (Capsicum annuumL.) in response toXanthomonas campestrispv.Vesicatoria

“…In plants, the hypersensitive response (HR) is a form of programmed cell death (PCD) at the site of pathogen infection, which is closely related to active resistance [42]. Previous studies showed that Bs2, Bs3 and Bs4 were only expressed in BS resistant pepper post Xcv inoculation, which could trigger HR [15,16]. Here, transcriptome profiling analysis results showed that bs2 (Capana09g000438) and bs3 (Capana02g001306) were not/hardly expressed in pepper leaves before and after Xcv inoculation.…”

“…To develop BS resistant commercially valuable cultivars through molecular breeding, four non-allelic hypersensitivity resistance genes, Bs1-Bs4, and two recessive non-hypersensitive resistance genes, Bs5 and Bs6, have been identified in pepper over the years [8,12]. Bs2, Bs3 and Bs4 are cloned, Bs2 and Bs3 develop molecular markers for marker-assisted selection (MAS) [5,[13][14][15][16]. Bs5 is positioned and its linked marker is also obtained [12].…”