Genome-Wide Identification and Expression Profiling of Tomato Invertase Genes Indicate Their Response to Stress and Phytohormones

Invertases (EC 3.2.1.26, INV) are indispensable for plant metabolism, development and stress response. Carbohydrate partitioning and the irreversible hydrolysis of sucrose into glucose and fructose in plants are driven by invertases. We performed a comprehensive analysis on the physico-chemical characteristics, chromosome localisation, exon–intron structures, motif distributions, evolutionary divergence and phylogenetic analysis, and tissue-specific spatio-temporal expression profiles of invertase genes under varied abiotic stressors and phytohormones. We identified twenty-four invertase genes (comprising nine cell wall (CWINV), two cell membrane (CMINV), eleven chloroplast (ChlINV), one cytosol (CyINV) and one vacuolar (VaINV)) in the tomato genome distributed on eight of the twelve chromosomes. The phylogenetic analysis clustered the invertase genes into two major clades. Segmental duplication contributed to the alkaline/neutral sub-domain expansion. The invertase genes were differentially expressed in fruits, roots, stems, leaves, flower buds and responded differentially to light, cold, drought, salinity stress and phytohormones (abscisic acid (ABA), gibberellic acid (GA), and indole-3 acetic acid (IAA)). Majority of the genes that were significantly up-regulated under the phytohormone treatments were consistently down-regulated in the stem, flowerbud and roots. The expression data reveals most of the cell wall and chloroplast-localised invertases were induced by phytohormones; while vacuolar and cytosol-localised invertases were markedly induced by abiotic stresses in the diverse tissues. The network interaction complex evidences that, most of the proteins were implicated in glycolysis, sucrose synthesis and/or pyrophosphate-fructose 6-phosphate 1-phosphotransferase activity. This study provides the groundwork for future functional analysis of invertase genes in tomato and other Solanaceae species.