Genes related to antioxidant metabolism are involved in Methylobacterium mesophilicum-soybean interaction

Abstract

The genus Methylobacterium is composed of pink-pigmented methylotrophic bacterial species that are widespread in natural environments, such as soils, stream water and plants. When in association with plants, this genus colonizes the host plant epiphytically and/or endophytically. This association is known to promote plant growth, induce plant systemic resistance and inhibit plant infection by phytopathogens. In the present study, we focused on evaluating the colonization of soybean seedling-roots by Methylobacterium mesophilicum strain SR1.6/6. We focused on the identification of the key genes involved in the initial step of soybean colonization by methylotrophic bacteria, which includes the plant exudate recognition and adaptation by planktonic bacteria. Visualization by scanning electron microscopy revealed that M. mesophilicum SR1.6/6 colonizes soybean roots surface effectively at 48 h after inoculation, suggesting a mechanism for root recognition and adaptation before this period. The colonization proceeds by the development of a mature biofilm on roots at 96 h after inoculation. Transcriptomic analysis of the planktonic bacteria (with plant) revealed the expression of several genes involved in membrane transport, thus confirming an initial metabolic activation of bacterial responses when in the presence of plant root exudates. Moreover, antioxidant genes were mostly expressed during the interaction with the plant exudates. Further evaluation of stress- and methylotrophic-related genes expression by qPCR showed that glutathione peroxidase and glutathione synthetase genes were up-regulated during the Methylobacterium-soybean interaction. These findings support that glutathione (GSH) is potentially a key molecule involved in cellular detoxification during plant root colonization. In addition to methylotrophic metabolism, antioxidant genes, mainly glutathione-related genes, play a key role during soybean exudate recognition and adaptation, the first step in bacterial colonization.

Seed Endophyte Microbiome of Crotalaria pumila Unpeeled: Identification of Plant-Beneficial Methylobacteria

“…Previously, it has been reported that Methylobacteria can colonise roots of different plant species [ 36 , 37 ], and also stems and leaves [ 38 , 39 ]. As also mentioned by Araújo et al [ 40 ], the initial step in the colonisation process seems to be the formation of biofilms on roots and on root hairs. Subsequently, the entrance into root cells occurs, as it has been demonstrated, that proliferating root hairs and side roots are important entry points for endophytic colonisation [ 41 , 42 , 43 ].…”

Metatranscriptomics and nitrogen fixation from the rhizoplane of maize plantlets inoculated with a group of PGPRs

“…In rice roots, Azospirillum lipoferum expressed genes related ROS detoxification and multidrug efflux pumps but nif genes were not induced (30). An antioxidant response has also been described in Methylobacterium when exposed to soybean root exudates (31). In rhizobia genes expressed in non-legume roots are involved in the transport of root derived nutrients and in legumes defense to plant phytoalexins (32).…”

Análises da expressão de genes do sistema de secreção na interação <i>Methylobacterium mesophilicum</i> SR 1.6/6 com a planta hospedeira.

“…Methylobacterium mesophilicum SR1.6/6 foi isolada endofiticamente de ramos de citros (ARAÚJO et al, 2002) e tem sido foco de estudos para o entendimento da sua interação com diferentes plantas hospedeiras, entre elas citros (ARAÚJO et al, 2002), vinca, tabaco (ANDREOTE et al, 2006, cana de açúcar (ROSSETO et al, 2011), arroz, eucalipto (DOURADO et al, 2013) e soja (ARAÚJO et al, 2015). Rosseto et al (2011) e Andreote et al (2006) observaram que M. mesophilicum SR 1.6/6 é capaz de formar biofilme sobre a planta hospedeira.…”

“…A análise do transcriptoma da interação M. mesophilicum com diferentes plantas hospedeiras mostrou que os exsudatos radiculares induzem a expressão de genes de resposta ao estresse oxidativo, seguido da indução de genes de adesão e biofilme durante a colonização da planta hospedeira (ARAÚJO et al, 2015;DOURADO et al, 2012). Adicionalmente, foram desenvolvidos estudos da interação de M. mesophilicum SR1.6/6 com a bactéria fitopatogênica Xylella fastidiosa (ARAÚJO et al, 2002;DOURADO et al, 2015;LACAVA et al, 2004) BLOEMBERG, 2002;MORRISSEY et al, 2004).…”

“…Methylobacterium spp., penetram na planta por meio de aberturas nas raízes e/ou folhas e são capazes de colonizar tecidos internos do hospedeiro, incluindo vasos condutores(GAN et al, 2012; HARDOIM et al 2015) e espaços intercelulares(QUADT-HALLMANN;KLOEPPER, 1996). No presente trabalho foi observar que M. mesophilicum SR1.6/6 coloniza de forma ativa a superfície das raízes de milho e citros, de forma semelhante ao já observado para plântulas de soja(ARAÚJO et al, 2015). Além disso, foi observado que os exsudados liberados pelas plantas (milho e citros) induzem um aumento no crescimento desta bactéria(Figura 8).…”