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. 2023 Dec 12;24(24):17408.
doi: 10.3390/ijms242417408.

Genome-Wide Identification and Expression Analysis of the SWEET Gene Family in Capsicum annuum L

Xiaowen Han  1   2 , Shuo Han  2 , Yongxing Zhu  2 , Yiqing Liu  2 , Shenghua Gao  1 , Junliang Yin  1   2 , Fei Wang  1 , Minghua Yao  1
Affiliations

Genome-Wide Identification and Expression Analysis of the SWEET Gene Family in Capsicum annuum L

Xiaowen Han et al. Int J Mol Sci. .

Abstract

Sugars will eventually be exported transporters (SWEETs) are a novel class of sugar transport proteins that play a crucial role in plant growth, development, and response to stress. However, there is a lack of systematic research on SWEETs in Capsicum annuum L. In this study, 33 CaSWEET genes were identified through bioinformatics analysis. The Ka/Ks analysis indicated that SWEET genes are highly conserved not only among peppers but also among Solanaceae species and have experienced strong purifying selection during evolution. The Cis-elements analysis showed that the light-responsive element, abscisic-acid-responsive element, jasmonic-acid-responsive element, and anaerobic-induction-responsive element are widely distributed in the promoter regions of CaSWEETs. The expression pattern analysis revealed that CaSWEETs exhibit tissue specificity and are widely involved in pepper growth, development, and stress responses. The post-transcription regulation analysis revealed that 20 pepper miRNAs target and regulate 16 CaSWEETs through cleavage and translation inhibition mechanisms. The pathogen inoculation assay showed that CaSWEET16 and CaSWEET22 function as susceptibility genes, as the overexpression of these genes promotes the colonization of pathogens, whereas CaSWEET31 functions as a resistance gene. In conclusion, through systematic identification and characteristic analysis, a comprehensive understanding of CaSWEET was obtained, which lays the foundation for further studies on the biological functions of SWEET genes.

Keywords: Ka/Ks; bioinformatics; microRNAs; protein characterization; subcellular localization.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Phylogenetic tree of C. annuum, A. thaliana, S. lycopersicoides, O. sativa SWEETs. Different colored circles represent different species.
Figure 2
Figure 2
Chromosome distribution of CaSWEETs. Chr stands for chromosome. The scale indicates the chromosome length (Mb).
Figure 3
Figure 3
Ka and Ks scatter diagram of homolog SWEET gene pairs among pepper and other Solanaceae species. The x-axis represents Ks, and the y-axis represents Ka.
Figure 4
Figure 4
Gene structure and conserved motif analysis. (A) Phylogenetic relationships. (B) Exon–intron structures. The green boxes represent the coding sequences (CDS), and the black lines represent the introns. (C) Conserved motif analysis. Different colors represent different motifs.
Figure 5
Figure 5
CaSWEET protein-predicted 3D models.
Figure 6
Figure 6
Analysis of cis-acting elements in CaSWEET promoters. Red squares indicate a high number of cis-elements, and white squares indicate a low number of cis-elements.
Figure 7
Figure 7
CaSWEET expression patterns under plant hormones, growth, and development, as well as abiotic stress treatments. Different colors in the legend represent different log2(TPM + 1) values, red represents the largest log2(TPM + 1) value, and blue represents the smallest value. CK: control (no further treatment); L: leaf; R: root; F: flower bud (cm is the length of the flower bud); P: perianth when flowers are fully open; O: ovary when the flower is fully open; STA: anther when the flower is fully open; FST: fruit; S: seed; T: placentation; ST: young seeds and placentation.
Figure 8
Figure 8
Sankey diagram for the relationships of miRNA targeting CaSWEETs transcripts. The three columns represent miRNA, mRNA, and the inhibition effect.
Figure 9
Figure 9
Subcellular location analysis of (B) CaSWEET16, (C) CaSWEET22, (D) CaSWEET31 was performed in N. benthamiana leaf. The free GFP was the control (A).
Figure 10
Figure 10
Influence of (A1,A3) CaSWEET16, (B1,B3) CaSWEET22, and (C1,C2) CaSWEET31 on disease resistance of N. benthamianaleaves. (A2,B2,C2) Statistical analysis of lesion diameter. Error bar represents standard deviation (SD). * Represents the significant level at p < 0.05, and ** represents the significant level at p < 0.05.
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