{"title":"Two TAL effectors of Xanthomonas citri promote pustule formation by directly repressing the expression of GRAS transcription factor in citrus.","authors":"Yichao Yan, Xiaomei Tang, Zhongfeng Zhu, Ke Yin, Yikun Zhang, Zhengyin Xu, Qiang Xu, Lifang Zou, Gongyou Chen","doi":"10.1186/s43897-024-00131-1","DOIUrl":null,"url":null,"abstract":"<p><p>Citrus bacterial canker (CBC), caused by Xanthomonas citri subsp. citri (Xcc), poses a significant threat to the citrus industry. Xcc employs the transcription activator-like effector (TALE) PthA4 to target the major susceptibility (S) gene CsLOB1 in citrus, promoting host susceptibility to bacterial canker. However, the contribution of other Xcc TALEs, aside from PthA4, to virulence remains underexplored. In this study, we characterized two PthA1 variants, designated PthA5 and PthA6, which facilitate Xcc infection in susceptible citrus species by promoting the formation of hypertrophy and hyperplasia symptoms. Both PthA5 and PthA6 bind directly to effector-binding elements (EBEs) in the promoter of CsGRAS9, suppressing its expression. CsGRAS9 negatively regulates Xcc growth in citrus and contributes to CBC resistance. Notably, natural variations in the EBEs of the FhGRAS9 promoter, a homolog of CsGRAS9 in Hong Kong kumquat, prevent Xcc from affecting FhGRAS9 expression. Using the PTG/Cas9 system, we generated proCsGRAS9-edited sweet orange lines #18-2 and #23, which contain 86-bp and 62-bp deletions in the EBE regions of the CsGRAS9 promoter. These mutant lines showed enhanced CsGRAS9 expression and increased resistance to CBC during Xcc infection. Several GA-related genes and CsTAC1, regulated by CsGRAS9, were also identified. This is the first report that TALEs act as repressors of a resistance gene to confer host susceptibility.</p>","PeriodicalId":29970,"journal":{"name":"Molecular Horticulture","volume":"5 1","pages":"30"},"PeriodicalIF":10.6000,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Molecular Horticulture","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1186/s43897-024-00131-1","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"HORTICULTURE","Score":null,"Total":0}
引用次数: 0
Abstract
Citrus bacterial canker (CBC), caused by Xanthomonas citri subsp. citri (Xcc), poses a significant threat to the citrus industry. Xcc employs the transcription activator-like effector (TALE) PthA4 to target the major susceptibility (S) gene CsLOB1 in citrus, promoting host susceptibility to bacterial canker. However, the contribution of other Xcc TALEs, aside from PthA4, to virulence remains underexplored. In this study, we characterized two PthA1 variants, designated PthA5 and PthA6, which facilitate Xcc infection in susceptible citrus species by promoting the formation of hypertrophy and hyperplasia symptoms. Both PthA5 and PthA6 bind directly to effector-binding elements (EBEs) in the promoter of CsGRAS9, suppressing its expression. CsGRAS9 negatively regulates Xcc growth in citrus and contributes to CBC resistance. Notably, natural variations in the EBEs of the FhGRAS9 promoter, a homolog of CsGRAS9 in Hong Kong kumquat, prevent Xcc from affecting FhGRAS9 expression. Using the PTG/Cas9 system, we generated proCsGRAS9-edited sweet orange lines #18-2 and #23, which contain 86-bp and 62-bp deletions in the EBE regions of the CsGRAS9 promoter. These mutant lines showed enhanced CsGRAS9 expression and increased resistance to CBC during Xcc infection. Several GA-related genes and CsTAC1, regulated by CsGRAS9, were also identified. This is the first report that TALEs act as repressors of a resistance gene to confer host susceptibility.
期刊介绍:
Aims
Molecular Horticulture aims to publish research and review articles that significantly advance our knowledge in understanding how the horticultural crops or their parts operate mechanistically. Articles should have profound impacts not only in terms of high citation number or the like, but more importantly on the direction of the horticultural research field.
Scope
Molecular Horticulture publishes original Research Articles, Letters, and Reviews on novel discoveries on the following, but not limited to, aspects of horticultural plants (including medicinal plants):
▪ Developmental and evolutionary biology
▪ Physiology, biochemistry and cell biology
▪ Plant-microbe and plant-environment interactions
▪ Genetics and epigenetics
▪ Molecular breeding and biotechnology
▪ Secondary metabolism and synthetic biology
▪ Multi-omics dealing with data sets of genome, transcriptome, proteome, metabolome, epigenome and/or microbiome.
The journal also welcomes research articles using model plants that reveal mechanisms and/or principles readily applicable to horticultural plants, translational research articles involving application of basic knowledge (including those of model plants) to the horticultural crops, novel Methods and Resources of broad interest.
In addition, the journal publishes Editorial, News and View, and Commentary and Perspective on current, significant events and topics in global horticultural fields with international interests.