Lectin genes in the Frankia alni genome

Abstract

Frankia alni strain ACN14a's genome was scanned for the presence of determinants involved in interactions with its host plant, Alnus spp. One such determinant type is lectin, proteins that bind specifically to sugar motifs. The genome of F. alni was found to contain 7 such lectin-coding genes, five of which were of the ricinB-type. The proteins coded by these genes contain either only the lectin domain, or also a heat shock protein or a serine-threonine kinase domain upstream. These lectins were found to have several homologs in Streptomyces spp., and a few in other bacterial genomes among which none in Frankia EAN1pec and CcI3 and two in strain EUN1f. One of these F. alni genes, FRAAL0616, was cloned in E. coli, fused with a reporter gene yielding a fusion protein that was found to bind to both root hairs and to bacterial hyphae. This protein was also found to modify the dynamics of nodule formation in A. glutinosa, resulting in a higher number of nodules per root. Its role could thus be to permit binding of microbial cells to root hairs and help symbiosis to occur under conditions of low Frankia cell counts such as in pioneer situations.

Genome Features of the Endophytic Actinobacterium Micromonospora lupini Strain Lupac 08: On the Process of Adaptation to an Endophytic Life Style?

“…638 [47] , Azoarcus BH72 [39] or the symbiotic actinobacterium Frankia sp . [48] have only a reduced set of cell-wall degrading enzymes.…”

Aspects of nitrogen-fixingActinobacteria, in particular free-living and symbioticFrankia

“…Lectins can be produced by the host or by the microorganisms to facilitate binding to the host (Lis and Sharon, ). Interestingly, recent investigations revealed that the genome of F. alni ACN14a contains five genes with a ricin B lectin domain (Pujic et al ., ), and a possible role for the lectins in Frankia was suggested to be to permit binding of microbial cells to root hairs to help symbiosis to occur under conditions of low Frankia cell numbers such as those in pioneer situations.…”

Antimicrobial activity and carbohydrate specificity of new mycelial lectins from Fusarium sp.

“…The structural and biochemical properties of distinct fungal lectins have been explored recently . The various physiological roles proposed for fungal lectins include identification of host during ectomycorrhizal symbiosis (Pujic et al 2012), facilitating association with algae and cyanobacteria in lichens (Diaz et al 2011;Singh & Walia, 2014) and yeast flocculation (Singh et al 2011).…”