Genome-wide identification of invertase genes in sweetpotato and its response to nitrogen and planting densities.

Abstract

Background: Invertases (INVs) included CWIN, CIN and VIN, are key enzymes in sucrose hydrolysis into glucose and fructose and essential for plant root development. Yet the effects of nitrogen and planting density on IbINVs expression remains unexplored in sweetpotato.

Results: This study identified 22 invertase (IbINV) genes in the sweetpotato genome and conducted comprehensive analyses of their subcellular localization, gene structure, and conserved motifs and domains. Gene Ontology functional and protein interaction network analysis suggested that IbCWIN1/2/5/6 potentially interact with HKL1/3, HXK2/3/4, and other proteins, significantly influencing carbohydrate metabolic functions and biological processes in sweetpotato. Transcriptome data revealed that IbCIN2 and IbVIN3 were highly expressed in fibrous root (FR) and potential storage root (PSR), while IbVIN4 exhibited high expression levels in storage roots (SR), and IbCWIN2 was highly expressed in both FR and SR. Moreover, the field experiments demonstrated that, compared with EN (180 kg N ha^-1) combined with LD (50,000 plant ha^- 1), MN (120 kg N ha^- 1) combined with MD (62,500 plant ha^- 1) enhanced storage roots number and weight. Notably, compared with LDEN treatment, IbCIN2, IbCWIN2, IbVIN3 and IbVIN4 under MDMN treatment were significantly upregulated, extremely significant differences at 15DAP, of which IbCIN2 showed a maximum of 23.24-fold change, showing a positive correlation with increased INV enzyme activity, glucose (GLc), and fructose (FRc) content. Additionally, screening of homologous genes showed that IbCIN2 is homologous to AtA/N-INVI and AtA/N-INVG, IbCWIN2, IbVIN3 and IbVIN4 are homologous to VACUOLAR, INVERTASE1 and BFRUCT4, with similar functions, further supporting their involvement in storage root formation and development.

Conclusion: These observations underscore the expansion of IbINVs in sweetpotato and provide a theoretical basis for optimizing the interaction between nitrogen application and planting density in sweetpotato, allowing for more efficient nitrogen use and improved growth.