Exploring the Potential Role of the TETRATRICOPEPTIDE THIOREDOXIN-LIKE Gene Family in Nitrogen-Fixing and Water-Restricted Soybean Plants

The TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are a plant-specific family proposed to function as peripheral membrane proteins that contribute to abiotic stress tolerance in Arabidopsis, likely by maintaining cell wall integrity through brassinosteroid signaling. In previous work of our group, we identified a GmTTL gene that showed differential abundance in the polysome-associated RNA (PAR) fraction in nitrogen-fixing soybean plants under water restriction (WR). This finding, together with the lack of knowledge about this gene family in soybean, prompted us to perform a genome-wide characterization of this family. In this work, using the Glycine max v4.0 proteome, we identified ten homologs (GmTTL1–GmTTL10) distributed across five chromosomes. Phylogenetic and structural analyses grouped these genes into three clades and revealed a highly conserved exon–intron organization, as well as conserved numbers and arrangements of TPR and TRXL motifs. Moreover, to investigate their potential biological functions, we reanalyzed by STRING the co-expression module enriched with 367 downregulated genes at the PAR level to which GmTTL7 belong. Interestingly, the protein–protein interaction (PPI) network analysis showed the over-representation of Gene Ontology (GO) terms associated with “cellular anatomical entity”, “membrane”, “cell periphery”, “cell wall modification”, “cell wall organization or biogenesis”, and “nitrate assimilation”. Notably, the PPI network revealed a novel predicted functional association between GmTTL and two nitrate reductase enzymes in nitrogen-fixing plants subjected to WR. This study provides a framework for future functional studies of GmTTL proteins and their contribution to abiotic stress adaptation in soybean.