Genome-wide identification of sweet potato U-Box E3 ubiquitin ligases and roles of IbPUB52 in negative regulation of drought stress.

The plant U-box (PUB) proteins, a family of ubiquitin ligases (E3) enzymes, are pivotal in orchestrating many biological processes and facilitating plant responses to environmental stressors. Despite their critical roles, exploring the PUB gene family's characteristics and functional diversity in sweet potato (Ipomoea batatas (L.) Lam.) has been notably limited. There were 81 IbPUB genes identified within the sweet potato genome, and they were categorized into eight distinct groups based on domain architecture, revealing a non-uniform distribution across the 15 chromosomes of I. batatas. The investigation of cis-acting elements has shed light on the potential of PUBs to participate in a wide array of biological processes, particularly emphasizing their role in mediating responses to abiotic stresses. Transcriptome profiles revealed that IbPUB genes displayed a wide range of expression levels among different tissues and were regulated by salt or drought stress. IbPUB52 has emerged as a gene of significant interest due to its induction by salt and drought stresses. Localization studies have confirmed the presence of IbPUB52 in both the nucleus and the cytoplasm, and its ubiquitination activity has been validated through rigorous in vitro and in vivo assays. Intriguingly, the heterogeneous expression of IbPUB52 in Arabidopsis resulted in decreased drought tolerance. The virus-induced gene silencing (VIGS) of IbPUB52 in sweet potatoes led to enhanced resistance to drought. This evidence suggests that IbPUB52 negatively regulates the drought tolerance of plants. The findings of this study are instrumental in advancing our comprehension of the functional dynamics of PUB E3 ubiquitin ligases in sweet potatoes.

Identification and functional characterization of the SUMO system in sweet potato under salt and drought stress.

Sumoylation is a crucial post-translation modification (PTM) that is the covalent attachment of SUMO molecules to the substrate catalyzed by enzyme cascade. Sumoylation is essential in almost every physiological process of plants, particularly in response to abiotic stress. However, little is known about sumoylation in sweet potato (Ipomoea batatas), the world's seventh most important food crop. In this study, 17 sweet potato SUMO system genes have been cloned and functionally characterized. Multiple sequence alignment and phylogenetic analysis showed sweet potato SUMO system proteins had conserved domains and activity sites. IbSUMOs, IbSAE1, and IbSCE1 were localized in the cytoplasm and nucleus. E3 SUMO ligases showed nuclear or punctate localization. In vitro sumoylation assay confirmed the catalytic activity of sweet potato SUMO system components. Heterologous expression of IbSIZ1 genes in Arabidopsis atsiz1 mutant rescued the defective germination and growth phenotype. IbSCE1a/b and IbSIZ1a/b/c were salt and drought responsive genes. Heterologous expression of IbSCE1a/b/c improved the drought tolerance of Arabidopsis thaliana, while IbSIZ1a/b/c significantly enhanced the salt and drought tolerance. Our findings define that the SUMO system in sweet potato shared with conserved function but also possessed specific characterization. The resources presented here would facilitate uncovering the significance of sumoylation in sweet potato.