Genome-wide analysis of expression quantitative trait loci(eQTLs)reveals the regulatory architecture of gene expression variation in the storage roots of sweet potato

Dissecting the genetic regulation of gene expression is critical for understanding phenotypic variation and species evolution.However,our understanding of the transcriptional variability in sweet potato remains limited.Here,we analyzed two publicly available datasets to explore the landscape of transcriptomic variations and its genetic basis in the storage roots of sweet potato.The comprehensive analysis identified a total of 724,438 high-confidence single nucleotide polymorphisms(SNPs)and 26,026 expressed genes.Expression quantitative trait locus(eQTL)analysis revealed 4408 eQTLs regulating the expression of 3646 genes,including 2261 local eQTLs and 2147 distant eQTLs.Two distant eQTL hotspots were found with target genes significantly enriched in specific functional classifications.By combining the information from regulatory network analyses,eQTLs and association mapping,we found that IbMYB1-2 acts as a master regulator and is the major gene responsible for the activation of anthocyanin biosynthesis in the storage roots of sweet potato.Our study provides the first insight into the genetic architecture of genome-wide expression variation in sweet potato and can be used to investigate the potential effects of genetic variants on key agronomic traits in sweet potato.

Overexpression of phosphatidylserine synthase IbPSS1 affords cellular Na+homeostasis and salt tolerance by activating plasma membrane Na^(+)/H^(+)antiport activity in sweet potato roots

Phosphatidylserine synthase(PSS)-mediated phosphatidylserine(PS)synthesis is crucial for plant development.However,little is known about the contribution of PSS to Na^(+)homeostasis regulation and salt tolerance in plants.Here,we cloned the IbPSS1 gene,which encodes an ortholog of Arabidopsis AtPSS1,from sweet potato(Ipomoea batatas(L.)Lam.).The transient expression of IbPSS1 in Nicotiana benthamiana leaves increased PS abundance.We then established an efficient Agrobacterium rhizogenes-mediated in vivo root transgenic system for sweet potato.Overexpression of IbPSS1 through this system markedly decreased cellular Na^(+)accumulation in salinized transgenic roots(TRs)compared with adventitious roots.The overexpression of IbPSS1 enhanced salt-induced Na^(+)/H^(+)antiport activity and increased plasma membrane(PM)Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the TRs.We confirmed the important role of IbPSS1 in improving salt tolerance in transgenic sweet potato lines obtained from an Agrobacterium tumefaciens-mediated transformation system.Similarly,compared with the wild-type(WT)plants,the transgenic lines presented decreased Na^(+)accumulation,enhanced Na^(+)exclusion,and increased PM Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the roots.Exogenous application of lysophosphatidylserine triggered similar shifts in Na^(+)accumulation and Na^(+)and Ca^(2+)fluxes in the salinized roots of WT.Overall,this study provides an efficient and reliable transgenic method for functional genomic studies of sweet potato.Our results revealed that IbPSS1 contributes to the salt tolerance of sweet potato by enabling Na^(+)homeostasis and Na^(+)exclusion in the roots,and the latter process is possibly controlled by PS reinforcing Ca^(2+)signaling in the roots.