IMAB - Institute for Multidisciplinary Research in Applied Biology

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Browsing IMAB - Institute for Multidisciplinary Research in Applied Biology by Author "Aguilera, Selene"

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    PublicationOpen Access
    The Pbo cluster from Pseudomonas syringae pv. phaseolicola NPS3121 is thermoregulated and required for phaseolotoxin biosynthesis
    (MDPI, 2021) Guardado-Valdivia, Lizeth; Chacón-López, Alejandra; Murillo Martínez, Jesús; Poveda Arias, Jorge; Hernández Flores, José Luis; Xoca-Orozco, Luis; Aguilera, Selene; Institute for Multidisciplinary Research in Applied Biology - IMAB
    The bean (Phaseolus vulgaris) pathogen Pseudomonas syringae pv. phaseolicola NPS3121 synthe-sizes phaseolotoxin in a thermoregulated way, with optimum production at 18 °C. Gene PSPPH_4550 was previously shown to be thermoregulated and required for phaseolotoxin bio-synthesis. Here, we established that PSPPH_4550 is part of a cluster of 16 genes, the Pbo cluster, included in a genomic island with a limited distribution in P. syringae and unrelated to the posses-sion of the phaseolotoxin biosynthesis cluster. We identified typical non-ribosomal peptide syn-thetase, and polyketide synthetase domains in several of the pbo deduced products. RT-PCR and the analysis of polar mutants showed that the Pbo cluster is organized in four transcriptional units, including one monocistronic and three polycistronic. Operons pboA and pboO are both es-sential for phaseolotoxin biosynthesis, while pboK and pboJ only influence the amount of toxin produced. The three polycistronic units were transcribed at high levels at 18 °C but not at 28 °C, whereas gene pboJ was constitutively expressed. Together, our data suggest that the Pbo cluster synthesizes secondary metabolite(s), which could participate in the regulation of phaseolotoxin biosynthesis.
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    PublicationOpen Access
    Two homologues of the global regulator Csr/Rsm redundantly control phaseolotoxin biosynthesis and virulence in the plant pathogen Pseudomonas amygdali pv. phaseolicola 1448A
    (MDPI, 2020) Ramírez Zapata, Diana; Ramos, Cayo; Aguilera, Selene; Bardají Goikoetxea, Leire; Martínez Gil, Marta; Murillo Martínez, Jesús; Institute for Multidisciplinary Research in Applied Biology - IMAB
    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.