Two Homologues of the Global Regulator Csr/Rsm Redundantly Control Phaseolotoxin Biosynthesis and Virulence in the Plant Pathogen Pseudomonas amygdali pv. phaseolicola 1448A

Microorganisms

Selene Aguilera¹  Diana Ramírez-Zapata²  Leire Bardaji²  Cayo Ramos³  Marta Martínez-Gil³  Jesús Murillo³ 

[1] Departamento de Química y Bioquímica, Instituto Tecnológico de Tepic, Colonia Lagos del Country, CP 63175 Tepic, Nayarit, Mexico;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;

关键词: phaseolotoxin;    phytotoxins;    GacS/GacA system;    two-component signal transduction system;    small regulatory RNAs;    Pseudomonas syringae;   

DOI  :  10.3390/microorganisms8101536

来源: DOAJ

【 摘 要 】

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 Pseudomonas amygdali pv. phaseolicola 1448A contains seven rsm genes, four of which are chromosomal. In RNAseq analyses, only rsmE was thermoregulated, with increased expression at 18 °C, whereas the antagonistic sRNAs rsmX1, rsmX4, rsmX5 and rsmZ showed increased levels at 28 °C. Only double rsmA-rsmE 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 hrpL and hrpA, and the flagellin gene, fliC. Biosynthesis of the phytotoxin phaseolotoxin by mutants in rsmA and rsmE was delayed, occurring only in older cultures, indicating that these rsm homologues act as inductors of toxin synthesis. Therefore, genes rsmA and rsmE 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.

【 授权许可】

Unknown