Comprehensive analyses of the citrus WRKY gene family involved in the metabolism of fruit sugars and organic acids

Abstract

Sugars and organic acids are the main factors determining the flavor of citrus fruit. The WRKY transcription factor family plays a vital role in plant growth and development. However, there are still few studies about the regulation of citrus WRKY transcription factors (CsWRKYs) on sugars and organic acids in citrus fruit. In this work, a genome-wide analysis of CsWRKYs was carried out in the citrus genome, and a total of 81 CsWRKYs were identified, which contained conserved WRKY motifs. Cis-regulatory element analysis revealed that most of the CsWRKY promoters contained several kinds of hormone-responsive and abiotic-responsive cis-elements. Furthermore, gene expression analysis and fruit quality determination showed that multiple CsWRKYs were closely linked to fruit sugars and organic acids with the development of citrus fruit. Notably, transcriptome co-expression network analysis further indicated that three CsWRKYs, namely, CsWRKY3, CsWRKY47, and CsWRKY46, co-expressed with multiple genes involved in various pathways, such as Pyruvate metabolism and Citrate cycle. These CsWRKYs may participate in the metabolism of fruit sugars and organic acids by regulating carbohydrate metabolism genes in citrus fruit. These findings provide comprehensive knowledge of the CsWRKY family on the regulation of fruit quality.

Analysis of sugar components and identification of SPS genes in citrus fruit development

“…To further understand the possible regulatory pathways of citrus sugar metabolism, we analysed the co-expression of CsSPSs based on our previous study ( Zhang et al., 2023a ). The results showed that all four CsSPSs were in the blue module (4,871 genes), which was positively correlated with the total sugar content, and the expression levels of most genes in the blue module increased with fruit development ( Figure 7A ).…”