Ramírez-Zapata Diana, Ramos Cayo, Aguilera Selene, Bardaji Leire, Martínez-Gil Marta, Murillo Jesús
Institute for Multidisciplinary Research in Applied Biology, Universidad Pública de Navarra, 31192 Mutilva Baja, Spain.
Área de Genética, Facultad de Ciencias, Universidad de Málaga, Campus Teatinos s/n, E-29010 Málaga, Spain.
Microorganisms. 2020 Oct 6;8(10):1536. doi: 10.3390/microorganisms8101536.
The widely conserved Csr/Rsm (carbon storage regulator/repressor of stationary-phase metabolites) post-transcriptional regulatory system controls diverse phenotypes involved in bacterial pathogenicity and virulence. Here we show that pv. phaseolicola 1448A contains seven genes, four of which are chromosomal. In RNAseq analyses, only was thermoregulated, with increased expression at 18 °C, whereas the antagonistic sRNAs , , and showed increased levels at 28 °C. Only double - mutants showed significantly altered phenotypes in functional analyses, being impaired for symptom elicitation in bean, including in planta growth, and for induction of the hypersensitive response in tobacco. Double mutants were also non-motile and were compromised for the utilization of different carbon sources. These phenotypes were accompanied by reduced mRNA levels of the type III secretion system regulatory genes and , and the flagellin gene, . Biosynthesis of the phytotoxin phaseolotoxin by mutants in and was delayed, occurring only in older cultures, indicating that these homologues act as inductors of toxin synthesis. Therefore, genes and act redundantly, although with a degree of specialization, to positively regulate diverse phenotypes involved in niche colonization. Additionally, our results suggest the existence of a regulatory molecule different from the Rsm proteins and dependent on the GacS/GacA (global activator of antibiotic and cyanide production) system, which causes the repression of phaseolotoxin biosynthesis at high temperatures.
广泛保守的Csr/Rsm（碳储存调节因子/稳定期代谢产物阻遏物）转录后调控系统控制着与细菌致病性和毒力相关的多种表型。在此，我们表明菜豆晕疫病菌1448A菌株含有7个基因，其中4个位于染色体上。在RNA测序分析中，只有在18℃时表达上调，表现出温度调节特性，而拮抗sRNA、、和在28℃时水平升高。在功能分析中，只有双突变体表现出显著改变的表型，在菜豆中引发症状（包括在植物体内生长）以及在烟草中诱导过敏反应方面受损。双突变体也无运动能力，并且在利用不同碳源方面存在缺陷。这些表型伴随着III型分泌系统调控基因和以及鞭毛蛋白基因的mRNA水平降低。和的突变体对植物毒素菜豆毒素的生物合成延迟，仅在较老的培养物中发生，这表明这些同源物作为毒素合成的诱导物。因此，基因和虽然具有一定程度的特异性，但以冗余方式发挥作用，正向调节与生态位定殖相关的多种表型。此外，我们的结果表明存在一种不同于Rsm蛋白且依赖于GacS/GacA（抗生素和氰化物产生的全局激活因子）系统的调控分子，它在高温下导致菜豆毒素生物合成的抑制。
