What question did this study set out to answer?

The study aims to identify and analyze the sucrose synthase (SUS) gene family across multiple Brassica species, focusing on their evolutionary and functional characteristics.

April 18, 2026Open Access

Genome-Wide Identification and Evolutionary Analysis of Sucrose Synthase (SUS) Gene Family in U’s Triangle Brassica Species

Key Points

The study aims to identify and analyze the sucrose synthase (SUS) gene family across multiple Brassica species, focusing on their evolutionary and functional characteristics.
Identified 65 SUS genes across six Brassica species.
Conducted phylogenetic analysis to classify genes into subfamilies.
Performed expression profiling to assess tissue specificity and environmental responses.
Validated findings through qRT-PCR and functional characterization in A. thaliana.
SUS genes classified into three subfamilies, with notable differences between diploid and polyploid species.
Brassica SUS family shows predominantly purifying selection with evidence of adaptive evolution in some genes.
Expression profiles indicated tissue-specific responses to hormones and abiotic stresses.
BnSUS3-2 enhanced osmotic and ionic stress tolerance in transgenic plants.

Abstract

The sucrose synthase (SUS) gene family plays a pivotal role in plant carbon metabolism, growth, and development. In this study, we identified 65 SUS genes across six Brassica species (B. rapa, B. nigra, B. oleracea, B. juncea, B. napus, and B. carinata), and systematically analyzed their structural characteristics, evolutionary history, and expression profiles. Phylogenetic analysis classified these genes into three subfamilies (SUSI, SUSII, and SUSIII). SUS4 orthologs (from SUSI subfamily) are completely lost in Brassica, and total SUS gene numbers are just 6–7 in Brassica diploid species, though the SUSIII subfamily exhibits significant expansion in Brassica polyploid species. Selection pressure analysis (Ka/Ks) revealed that the Brassica SUS family has primarily undergone purifying selection, although certain members show evidence of adaptive evolution. Comprehensive expression profiling and qRT-PCR validation demonstrated the functional diversification of BnSUS genes in tissue specificity and responses to hormonal and abiotic stimuli. SUSI genes BnSUS1-1/2/3/4 are predominantly expressed in vegetative tissues and flowers; SUSII genes BnSUS2-1/2 and BnSUS3-1/2 are reproductive-organ-specific, while SUSIII genes BnSUS5-1/2 and BnSUS6-1/2/3/4 show young-plant-specific weak expression. BnSUS family genes are generally upregulated by ABA, TZ and GA but downregulated by IAA, ACC, BL and JA. Salt, drought, freezing and cold mainly upregulate the BnSUS family, heat downregulates it, and osmotic stress exerts both effects. Correspondingly, Brassica SUS promoters are enriched with light-responsive (G-box, Box-4), hormone-responsive (ABRE, CGTCA-motif) and anaerobic-induction (ARE) elements. Functional characterization demonstrated that the ABA-responsive gene BnSUS3-2 significantly improved tolerance to osmotic and ionic stresses by promoting root growth in transgenic A. thaliana seedlings. These findings underscore the essential roles of BnSUS genes in maintaining cellular homeostasis and provide a theoretical foundation for the genetic improvement of carbon metabolism and stress resilience in Brassica crops.

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Cite This Study

Huang et al. (Thu,) studied this question.

synapsesocial.com/papers/69e31fcb40886becb653ee5f https://doi.org/https://doi.org/10.3390/plants15081224

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