Comprehensive genome-wide identification and analysis of the glycolate oxidase (GLO) gene family in tomato (Solanum lycopersicum L.) during biotic stress and fruit development stages

GLO/GOX represents an essential enzyme in photorespiratory metabolism in plants, catalyzing glycolate oxidation to glyoxylate and producing H₂O₂, a signaling molecule involved in various physiological processes and defense mechanisms. Here, we identified and analyzed six putative glycolate oxidase genes in tomatoes and classified them into three groups based on phylogenetic analysis, gene structure, and motif composition. Our data showed that tandem duplication contributed mainly to expanding the GLO gene families in tomatoes. The promoter analysis identified the specific cis-regulatory elements (CREs) related to stress, light, hormone, and development. Gene ontology analysis found that all six SlGLO genes are mainly associated with oxidoreductase activity. Transcriptome analysis of the interactions of tomatoes with AMF emphasized the role of SlGLO genes in fruit nutrition improvement. The gene expression varied among different SlGLOs. Specifically, SlGLO2 showed the lowest expression, while SlGLO1 and SlGLO3 were highly expressed in red fruits; SlGLO6 was highly expressed in green but unripe in red fruits. Alternatively, SlGLO4 and SlGLO5 were the highest, indicating involvement in the potential amelioration of fruit quality. Gene expression analysis using qRT-PCR showed that SlGLOs are differentially expressed across different organs and at various stages of fruit development, implicating this gene family in plant development and physiology. Furthermore, RNA-seq comparison under biotic stress demonstrated differential expression within different tomato cultivars. SlGLO1 and SlGLO2 were moderately expressed, while SlGLO3 expression decreased in infected roots. SlGLO4 and SlGLO6 were upregulated within the resistant Mogeor cultivars, indicating their involvement in pathogen-associated transcriptional regulation. Overall, our study demonstrates the multifaceted role of SlGLO genes in stress response, development, and fruit quality improvement.