Sugarcane is a major sugar-producing crop, which contributed 80% of the world’s sugar in 2010. Saccarhum officinarum is a domestic species with high sugar content, while, Saccarhum spontaneum is a wild species with stress tolerance. The highly complex polyploid genome of modern sugarcane cultivars arose from the interspecific hybridization between S. officinarum and S. spontaneum. Sucrose synthase (SUS) is a key enzyme for sucrose metabolism in plants, where activity is bidirectional: both synthetic and separate. In this study, nine genomic sequences of S. officinarum and eight genomic sequences of S. spontaneum for five SUS genes were identified. Phylogenetic analysis showed that the Saccharum SUS3 and SUS5 genes were generated from ρ duplication, SUS1 and SUS2 were duplicated after the split of dicot and monocot species, and SUS4 was retained from the last common ancestor before the origination of Angiospermae. The gene structure and Ka/Ks analysis suggested the functional constraint of SUS genes in the two Saccharum species. Gene expression based on RNA-seq analysis revealed that SUS1was dominantly expressed in source tissues including the internodes and the basal zone of the leaves, SUS2 was detectable in all tissues examined, and the remaining three SUS genes were expressed at low levels in the examined tissues, indicating SUS1 is the key member involved in sucrose accumulation. In addition, SUS genes were observed to be present at higher expression levels in S. officinarum than in S. spontaneum, while SUS2 presented different expression patterns during the circadian rhythm in S. spontaneum and S. officinarum, suggesting the two SUS genes contribute to the differential sugar levels in these species. Our comprehensive study in Saccharum provides the foundations for further functional studies of the SUS gene family.

中文翻译：

---

蔗糖和自发性蔗糖SUS基因家族的比较分析

甘蔗是主要的产糖作物，2010年占全球糖的80％。蔗糖是一种国内食糖含量高的物种，而自发糖荚is是具有抗逆性的野生物种。现代甘蔗品种的高度复杂的多倍体基因组来自于S. officinarum和S. spontaneum之间的种间杂交。蔗糖合酶（SUS）是植物中蔗糖代谢的关键酶，其活性是双向的：合成的和单独的。在这项研究中，针对五个SUS的九种链球菌基因组序列和自发链球菌的八个基因组序列基因被鉴定。系统发育分析表明，蔗糖的SUS3和SUS5基因是由ρ重复产生的，双子叶植物和单子叶植物物种分裂后复制了SUS1和SUS2，在被子植物起源之前，SUS4和SUS4被保留在最后一个祖先。基因结构和Ka / Ks分析表明了两个蔗糖物种中SUS基因的功能限制。基于RNA-seq分析的基因表达表明，SUS1在包括叶节间和叶基区在内的来源组织中占主导地位，在所有检查过的组织中均可检测到SUS2，其余三个SUS基因在检查过的组织中低水平表达，表明SUS1是参与蔗糖积累的关键成员。另外，SUS观察基因是存在于更高的表达水平S.良姜比割手密，而SUS2在昼夜节律期间呈现不同的表达模式割手密和S.良姜，提示两个SUS基因有助于这些物种中的糖含量差异。我们对蔗糖的综合研究为SUS基因家族的进一步功能研究提供了基础。