Genome-Wide Identification, Expression, and Activity Analysis of Alkaline/Neutral Invertase Gene Family from Cassava (Manihot esculenta Crantz)

Alkaline/neutral invertase comprises a family of enzymes that catalyze the irreversible hydrolysis of sucrose into glucose and fructose. They play a crucial role in carbohydrate partitioning and developmental processes of plants. In this study, we genome-wide identified 11 alkaline/neutral invertase family genes (MeNINVs) from the cassava genome. Based on phylogeny, MeNINVs could be classified into alpha and beta groups. The alpha group genes are encoded by six exons (MeNINV1, 6, 7, 8, and 10) or four exons (MeNINV9), whereas the beta group genes are encoded by four exons (MeNINV2, 3, 4, and nINV1) or five exons (MeNINV5). Their catalytic residues of motifs 2 and 4 for sucrose hydrolysis locate in all MeNINVs. qRT-PCR analysis has demonstrated that all MeNINVs are highly expressed in floral organs. During tuber development, MeNINV1, 6, 10, and nINV1 are strongly expressed in source tissues (leaves), and MeNINV1 and nINV1 also play an important role in sink organs (tuber). Activity analysis of alkaline/neutral invertase and determination of sucrose content in source and sink organs of cassava indicates that lower efficiency of sucrose hydrolysis in source organs (leaves) and higher efficiency in sink organs (tuber) are beneficial sucrose to transport from source to sink organs.