Genome-Wide Identification and Expression Analysis of SWEET Family Genes in Sweet Potato and Its Two Diploid Relatives

Sugar Will Eventually be Exported Transporter (SWEET) proteins are key transporters in sugar transportation. They are involved in the regulation of plant growth and development, hormone crosstalk, and biotic and abiotic stress responses. However, SWEET family genes have not been explored in the sweet potato. In this study, we identified 27, 27, and 25 SWEETs in cultivated hexaploid sweet potato (Ipomoea batatas, 2n = 6x = 90) and its two diploid relatives, Ipomoea trifida (2n = 2x = 30) and Ipomoea triloba (2n = 2x = 30), respectively. These SWEETs were divided into four subgroups according to their phylogenetic relationships with Arabidopsis. The protein physiological properties, chromosome localization, phylogenetic relationships, gene structures, promoter cis-elements, protein interaction networks, and expression patterns of these 79 SWEETs were systematically investigated. The results suggested that homologous SWEETs are differentiated in sweet potato and its two diploid relatives and play various vital roles in plant growth, tuberous root development, carotenoid accumulation, hormone crosstalk, and abiotic stress response. This work provides a comprehensive comparison and furthers our understanding of the SWEET genes in the sweet potato and its two diploid relatives, thereby supplying a theoretical foundation for their functional study and further facilitating the molecular breeding of sweet potato

Number of genes enriched in each module.

<p>Number of genes enriched in each module.</p

Statistics of splicing results of transcriptome sequencing data.

<p>Statistics of splicing results of transcriptome sequencing data.</p

Phylogenetic analysis of ABI-like and Ca²⁺ ATPase genes.

<p>(A) Evolutionary analysis of ABI-like genes in K14, KT1, and Tri with their homologs from different plant species and with ABI proteins from Arabidopsis. (B) Evolutionary analysis of Ca²⁺-ATPase genes in K14, KT1, and Tri with Arabidopsis homologs. Length of branch lines indicates the extent of divergence.</p

Top 20 genes enriched in light yellow module.

<p>Top 20 genes enriched in light yellow module.</p

WGCNA module building, Hubgenes cluster analysis, and EigenGene expression statistics.

<p>(A, B) Hierarchical clustering of co-expression data. (C) Heatmap cluster of Hubgenes from cyan module. (D) Heatmap cluster of Hubgenes from light yellow module. (E) Eigengenes expression pattern in cyan module. (F) Eigengenes expression pattern in light yellow module.</p

Top 20 genes enriched in cyan module.

<p>Top 20 genes enriched in cyan module.</p

Module correlation coefficients from weighted gene co-expression network analysis.

<p>Variables shown on x-axis are genotype (KT1, K14, Tri), time, duration of drought stress treatment (0, 6, 12, 24 h), and difference between two treatment times (0, 6 h; 6, 12 h; 12, 24 h).</p

Involvement of an ABI-like protein and a Ca²⁺-ATPase in drought tolerance as revealed by transcript profiling of a sweetpotato somatic hybrid and its parents <i>Ipomoea batatas</i> (L.) Lam. and <i>I</i>. <i>triloba</i> L.

<div><p>Previously, we obtained the sweetpotato somatic hybrid KT1 from a cross between sweetpotato (<i>Ipomoea batatas</i> (L.) Lam.) cv. Kokei No. 14 and its drought-tolerant wild relative <i>I</i>. <i>triloba</i> L. KT1 not only inherited the thick storage root characteristic of Kokei No. 14 but also the drought-tolerance trait of <i>I</i>. <i>triloba</i> L. The aim of this study was to explore the molecular mechanism of the drought tolerance of KT1. Four-week-old <i>in vitro</i>-grown plants of KT1, Kokei No. 14, and <i>I</i>. <i>triloba</i> L. were subjected to a simulated drought stress treatment (30% PEG6000) for 0, 6, 12 and 24 h. Total RNA was extracted from samples at each time point, and then used for transcriptome sequencing. The gene transcript profiles of KT1 and its parents were compared to identify differentially expressed genes, and drought-related modules were screened by a weighted gene co-expression network analysis. The functions of ABI-like protein and Ca²⁺-ATPase, two proteins screened from the cyan and light yellow modules, were analyzed in terms of their potential roles in drought tolerance in KT1 and its parents. These analyses of the drought responses of KT1 and its somatic donors at the transcriptional level provide new annotations for the molecular mechanism of drought tolerance in the somatic hybrid KT1 and its parents.</p></div

Heatmap clustering of unigenes and Venn diagram of differentially expressed genes (DEGs) in 24 samples.

<p>(A) Heatmap clustering of unigenes in 24 samples. (B-D) Venn diagrams of up-regulated and down-regulated DEGs under drought stress at 6 h, 12 h and 24 h in K14 (B), KT1 (C) and Tri (D). (E-G) Venn diagrams of up-regulated and down-regulated DEGs under drought stress in K14, KT1 and Tri at 6 h (E), 12 h (F) and 24 h (G). Left, up-regulated DEGs; right, down-regulated DEGs.</p