AUTHOR=Lu Wen , Hao Wenhui , Liu Kexin , Liu Jiahuan , Yin Chunmei , Su Yujiao , Hang Zhiyu , Peng Bin , Liu Huan , Xiong Bo , Liao Ling , He Jiaxian , Zhang Mingfei , Wang Xun , Wang Zhihui 

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

JOURNAL=Frontiers in Plant Science

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1372809

DOI=10.3389/fpls.2024.1372809

ISSN=1664-462X

ABSTRACT=<p>Sugar is a primary determinant of citrus fruit flavour, but undergoes varied accumulation processes across different citrus varieties owing to high genetic variability. Sucrose phosphate synthase (SPS), a key enzyme in glucose metabolism, plays a crucial role in this context. Despite its significance, there is limited research on sugar component quality and the expression and regulatory prediction of <italic>SPS</italic> genes during citrus fruit development. Therefore, we analysed the sugar quality formation process in ‘Kiyomi’ and ‘Succosa’, two citrus varieties, and performed a comprehensive genome-wide analysis of citrus <italic>CsSPSs</italic>. We observed that the accumulation of sugar components significantly differs between the two varieties, with the identification of four <italic>CsSPSs</italic> in citrus. <italic>CsSPS</italic> sequences were highly conserved, featuring typical SPS protein domains. Expression analysis revealed a positive correlation between <italic>CsSPS</italic> expression and sugar accumulation in citrus fruits. However, <italic>CsSPS</italic> expression displays specificity to different citrus tissues and varieties. Transcriptome co-expression network analysis suggests the involvement of multiple transcription factors in shaping citrus fruit sugar quality through the regulation of <italic>CsSPSs</italic>. Notably, the expression levels of four <italic>CsWRKYs</italic> (<italic>CsWRKY2</italic>, <italic>CsWRKY20</italic>, <italic>CsWRKY28</italic>, <italic>CsWRKY32</italic>), were significantly positively correlated with <italic>CsSPSs</italic> and <italic>CsWRKY20</italic> might can activate sugar accumulation in citrus fruit through <italic>CsSPS2</italic>. Collectively, we further emphasize the potential importance of <italic>CsWRKYs</italic> in citrus sugar metabolism, our findings serve as a reference for understanding sugar component formation and predicting <italic>CsSPS</italic> expression and regulation during citrus fruit development.</p>