Long-Term Soil Drought Limits Starch Accumulation by Altering Sucrose Transport and Starch Synthesis in Sweet Potato Tuberous Root

Abstract

In this study, the influences of long-term soil drought with three levels [soil-relative water content (SRWC) (75 ± 5)%, as the control; SRWC (55 ± 5)%, mild drought; SRWC (45 ± 5)%, severe drought] were investigated on sucrose-starch metabolism in sweet potato tuberous roots (TRs) by pot experiment. Compared to the control, drought stress increased soluble sugar and sucrose content by 4–60% and 9–75%, respectively, but reduced starch accumulation by 30–66% through decreasing the starch accumulate rate in TRs. In the drought-treated TRs, the inhibition of sucrose decomposition was attributed to the reduced activities of acid invertase (AI) and (AKI) and the IbA-INV3 expression, rather than sucrose synthase (SuSy), consequently leading to the increased sucrose content in TRs. In addition, starch synthesis was inhibited mainly by reducing ADP-glucose pyrophosphorylase (AGPase), granular starch synthase (GBSS) and starch branching enzyme (SBE) activities in TRs under drought stress, and AGPase was the rate-limiting enzyme. Furthermore, soil drought remarkably up-regulated the IbSWEET11, IbSWEET605, and IbSUT4 expressions in Jishu 26 TRs, while it down-regulated or had no significant differences in Xushu 32 and Ningzishu 1 TRs. These results suggested that the sucrose-loading capability in Jishu 26 TRs were stronger than that in Xushu 32 and Ningzishu 1 TRs. Moreover, IbA-INV3, IbAGPS1, IbAGPS2, IbGBSSI and IbSBEII play important roles in different drought-tolerant cultivars under drought stress.

Expression Profiling of Salt-Responsive Genes and Transcription Factors in Leaf Transcriptome of Arabidopsis thaliana

“…NFYC3's gene function, encompassing DNA damage repair, cell cycle regulation and abscisic acid signaling [80], does not readily correlate with RFS6, suggesting an incidental concordance. Lastly, cluster 67 featured the salt-responsive starch synthase (SSY1) gene acting on starch biosynthesis of starch granules in seeds with an uncertain role during drought stress [89] and the ethylene-responsive transcription factor ERF55 (ERF55) TF gene. While SSY1's regulation under salt stress in Arabidopsis lacks precedent, ERF55's role in this context remains elusive.…”

The Production of Coating Film with Sweet Potato Starch and Carboxymethylcellulose from Water Hyacinth on Storage Life Extension of Mango (Mangifera indica L.)

“…Sweet potato (Ipomea batatas (L.) Lam) is one of the most important crops due to its abundance, renewability, biodegradability, non-toxicity and low cost [11]. Its root tuber is rich in starch [12]. However, coating fruits with only one type of starch may result in high water permeability, and brittleness, limiting their processability and applicability [13].…”

Genome-Wide Identification and Expression Analysis of the Starch Synthase Gene Family in Sweet Potato and Two of Its Closely Related Species

“…Inhibition of IbSSII gene expression by RNA interference dramatically alters the basic structure of starch and thus its functional properties [30]. Furthermore, IbGBSSI plays an important role in different drought-tolerant cultivars under drought stress [31]. Therefore, SSs may be involved in starch synthesis and abiotic stress responses in sweet potato.…”