Background Sorghum bicolor (L.) is an important bioenergy source. The stems of sweet sorghum function as carbon sinks and accumulate large amounts of sugars and lignocellulosic biomass and considerable amounts of starch, therefore providing a model of carbon allocation and accumulation for other bioenergy crops. While omics data sets for sugar accumulation have been reported in different genotypes, the common features of primary metabolism in sweet genotypes remain unclear. To obtain a cohesive and comparative picture of carbohydrate metabolism between sorghum genotypes, we compared the phenotypes and transcriptome dynamics of sugar-accumulating internodes among three different sweet genotypes (Della, Rio, and SIL-05) and two non-sweet genotypes (BTx406 and R9188). Results Field experiments showed that Della and Rio had similar dynamics and internode patterns of sugar concentration, albeit distinct other phenotypes. Interestingly, cellulose synthases for primary cell wall and key genes in starch synthesis and degradation were coordinately upregulated in sweet genotypes. Sweet sorghums maintained active monolignol biosynthesis compared to the non-sweet genotypes. Comparative RNA-seq results support the role of candidate Tonoplast Sugar Transporter gene (TST), but not the Sugars Will Eventually be Exported Transporter genes (SWEETs) in the different sugar accumulations between sweet and non-sweet genotypes. Conclusions Comparisons of the expression dynamics of carbon metabolic genes across the RNA-seq data sets identify several candidate genes with contrasting expression patterns between sweet and non-sweet sorghum lines, including genes required for cellulose and monolignol synthesis (CesA, PTAL, and CCR), starch metabolism (AGPase, SS, SBE, and G6P-translocator SbGPT2), and sucrose metabolism and transport (TPP and TST2). The common transcriptome features of primary metabolism identified here suggest the metabolic networks contributing to carbon sink strength in sorghum internodes, prioritize the candidate genes for manipulating carbon allocation with bioenergy purposes, and provide a comparative and cohesive picture of the complexity of carbon sink strength in sorghum stem.

中文翻译：

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常见的代谢网络有助于高粱节间的碳汇强度：对生物能源改进的影响。


背景高粱（L.）是一种重要的生物能源。甜高粱的茎具有碳汇功能，积累大量的糖和木质纤维素生物质以及大量的淀粉，因此为其他生物能源作物提供了碳分配和积累的模型。尽管已经报道了不同基因型中糖积累的组学数据集，但甜味基因型中初级代谢的共同特征仍不清楚。为了获得高粱基因型之间碳水化合物代谢的连贯和比较图，我们比较了三种不同甜基因型（Della、Rio和SIL-05）和两种非甜基因型（BTx406和R9188）。结果 田间实验表明，Della 和 Rio 具有相似的糖浓度动态和节间模式，尽管其他表型不同。有趣的是，初级细胞壁的纤维素合酶和淀粉合成和降解的关键基因在甜味基因型中协调上调。与非甜基因型相比，甜高粱保持了活跃的木质醇单体生物合成。比较 RNA-seq 结果支持候选液泡膜糖转运蛋白基因 (TST) 的作用，但不支持糖最终会导出转运蛋白基因 (SWEET) 在甜味和非甜味基因型之间不同糖积累中的作用。 结论 通过对 RNA-seq 数据集碳代谢基因表达动态的比较，确定了几个在甜高粱品系和非甜高粱品系之间具有对比表达模式的候选基因，包括纤维素和木质素单体合成所需的基因（CesA、PTAL 和 CCR） 、淀粉代谢（AGPase、SS、SBE 和 G6P 转运蛋白 SbGPT2）以及蔗糖代谢和运输（TPP 和 TST2）。这里确定的初级代谢的常见转录组特征表明，代谢网络有助于高粱节间碳汇强度，优先考虑以生物能源为目的操纵碳分配的候选基因，并提供高粱碳汇强度复杂性的比较和凝聚力图景干。