DESCRIPTION OF A NOVEL ENDOPHYTIC PLANT GROWTH-PROMOTING Pseudomonas SPECIES WITH THE ABILITY TO MODULATE STOMATAL APERTURE, A TRAIT NOT PREVIOUSLY REPORTED FOR NON-PATHOGENIC BACTERIA

GONZALEZ, ME; CASTAGNO, N; SANNAZZARO, AI; ESTRELLA, MJ; RÍOS, C; GUDESBLAT, GE; PIECKENSTAIN, FL

Congreso; XVIII Congreso Argentino de Microbiología General; 2023

 A previous bioprospection of endophytic bacteria associated to horticulturalcrops identified several strains that exerted biological control of tomato diseasescaused by the phytopathogenic fungus Botrytis cinerea and the phytopathogenicbacterium Pseudomonas syringae pv tomato and also showed plant growth promotingtraits (1). One of these strains, designed as NT2 and assigned to the genusPseudomonas based on 16S-rRNA gene sequencing, attracted our attention becauseof its ability to both inhibit fungal growth and suppress plant stomatal immunity throughthe production of diffusible signals. Suppression of stomatal immunity could provide ameans for endophytic leaf colonization and might also affect the regulation of planttranspiration through stomata. Modulation of stomatal aperture was reported forphytopathogenic bacteria belonging to the genera Pseudomonas and Xanthomonas(2,3), but was not shown for plant growth-promoting bacteria so far.The aim of this work was to establish the taxonomical identity of Pseudomonassp. NT2. A preliminary taxonomical analysis showed that, despite being closely relatedto Pseudomonas veronii DSM11631 T and Pseudomonas fildesensis KG01 T ,Pseudomonas sp. NT2 belongs to a separate clade, along with other Pseudomonasstrains originally isolated by our group during the above mentioned bioprospection.Next, Pseudomonas sp. NT2 genome was fully sequenced and assembled.Phylogenomic and multilocus sequence analysis of housekeeping genes gyrB, rpoDand rpoB confirmed that strain NT2 belongs to a distinct clade within the genusPseudomonas. Indexes obtained after in silico DNA-DNA hybridization and averagenucleotide identity-based comparison of Pseudomonas sp. NT2 genome with closelyrelated Pseudomonas species were below the threshold for species delineation. As awhole, our results suggest that NT2 and other strains isolated during the initialbioprospection correspond to a novel Pseudomonas species, for which NT2 isproposed as the type strain. To our knowledge, Pseudomonas sp. NT2 is the firstexample of a plant growth-promoting bacteria able to modulate stomatal aperture.Thus, Pseudomonas sp. NT2 might serve as a model for further studying the possiblerole of modulation of stomatal aperture in endophytic colonization of plant leaves bynon-pathogenic bacteria, as well as its effects on gas exchange of the host plant.