Genome-wide investigation of sucrose synthase gene family in pineapple: Characterization and expression profile analysis during fruit development

Sucrose content influences the flavour and quality of fruits. Sucrose synthase (SUS; EC 2.4.1.13) mediates the reversible conversion of uridine diphosphate and sucrose to uridine diphosphate-glucose and fructose. Although genome-wide analyses of <i>SUS</i> gene families exist for various species, such studies are lacking for pineapple. The specific <i>SUS</i> gene(s) involved in sucrose metabolism during pineapple development remain unknown. This study identified six <i>SUS</i> genes (<i>AcSUS1–6</i>) and analysed their chromosomal locations, synteny, structure, motif composition, sequence alignments, and phylogenetic relationships. Gene promoter analysis revealed a predominance of light-response elements in the <i>AcSUS</i> gene family. <i>AcSUS1</i> was predominantly expressed in the peduncle, pericarp, and core, whereas <i>AcSUS4</i> was highly expressed in the flesh. The levels of sucrose, glucose, and fructose increase during pineapple fruit development. Further gene expression analysis indicated that <i>AcSUS2</i>, <i>AcSUS3</i>, and <i>AcSUS5</i> were down-regulated during this period. These results suggest that <i>AcSUS2</i>, <i>AcSUS3</i>, and <i>AcSUS5</i> may modulate sucrose breakdown in pineapple. This study contributes to our understanding of <i>SUS</i> gene function in regulating sucrose metabolism and offers valuable theoretical guidance for the genetic improvement of pineapples.

蔗糖含量直接影响果实的风味与品质。蔗糖合酶（sucrose synthase, SUS; EC 2.4.1.13）可催化尿苷二磷酸与蔗糖发生可逆反应，生成尿苷二磷酸葡萄糖和果糖。尽管已有多个物种完成了SUS基因家族的全基因组分析，但针对菠萝的此类研究仍付阙如。目前，菠萝发育过程中参与蔗糖代谢的特异性SUS基因仍未被探明。本研究共鉴定出6个SUS基因（AcSUS1–6），并对其染色体定位、共线性关系、基因结构、基序组成、序列比对及系统发育关系展开了系统分析。基因启动子分析结果显示，AcSUS基因家族的启动子区域以光响应元件占比最高。AcSUS1主要在花序轴、果皮及果芯中表达，而AcSUS4则在果肉中呈显著高表达。在菠萝果实发育进程中，蔗糖、葡萄糖及果糖的含量均呈逐步上升趋势。进一步的基因表达分析表明，AcSUS2、AcSUS3及AcSUS5在此期间表达量显著下调。上述结果提示，AcSUS2、AcSUS3及AcSUS5可能参与调控菠萝体内的蔗糖分解过程。本研究有助于深化对SUS基因家族调控蔗糖代谢功能的认知，同时可为菠萝的遗传改良提供重要的理论指导。