Transcriptome and metabolome reveal distinct carbon allocation patterns during internode sugar accumulation in different sorghum genotypes

First author: Yin Li; Affiliations: Rutgers, The State University of New Jersey (罗格斯新泽西州立大学): Piscataway, USA

Corresponding author: Joachim Messing

Sweet sorghum accumulates large amounts of soluble sugar in its stem. However, a system‐ased understanding of this carbohydrate allocation (碳水化合物分配) process is lacking. Here, we compared the dynamic transcriptome and metabolome between the conversion line R9188 and its two parents, sweet sorghum RIO and grain sorghum BTx406 that have contrasting sugar‐accumulating phenotypes. We identified two features of sucrose metabolism, stable concentrations of sugar phosphates in RIO and opposite trend of trehalose‐6‐phosphate (T6P; 海藻糖6磷酸) between RIO versus R9188/BTx406. Integration of transcriptome and metabolome revealed R9188 is partially active in starch metabolism (淀粉代谢) together with medium sucrose level, whereas sweet sorghum had the highest sucrose concentration and remained highly active in sucrose, starch, and cell wall metabolism post‐anthesis (开花后). Similar expression pattern of genes involved in sucrose degradation decreased the pool of sugar phosphates for precursors of starch and cell wall synthesis in R9188 and BTx406. Differential T6P signal between RIO versus R9188/BTx406 is associated with introgression of T6P regulators from BTx406 into R9188, including C‐group bZIP and trehalose 6‐phosphate phosphatase (TPP; 海藻糖6磷酸磷酸酶). The inverted T6P signaling in R9188 appears to downregulate sucrose and starch metabolism partly through transcriptome reprogramming, whereas introgressed metabolic genes could be related to reduced cell wall metabolism. Our results show that coordinated primary metabolic pathways lead to high sucrose demand and accumulation in sweet sorghum, providing us with targets for genetic improvements of carbohydrate allocation in bioenergy crops.

甜高粱可以在其茎秆中积累大量的可溶性糖分。然而，目前我们仍然缺乏对这个碳水化合物分配过程的系统性理解。本文比较了渐渗系R9188和它的两个亲本甜高粱RIO和食用高粱BTx406（低糖）茎秆中转录组和代谢组在不同时期的变化。甜高粱RIO和食用高粱BTx406在茎秆糖分积累方面的表型差异明显。通过比较渐渗系和其亲本，我们发现甜高粱茎秆的蔗糖代谢具有两个特点：一是甜高粱中糖磷酸浓度稳定；二是甜高粱与BTx406和R9188有着相反的海藻糖6磷酸变化。代谢组和转录组数据联合分析显示渐渗系R9188在茎秆累积中等浓度的蔗糖并且其部分淀粉代谢相关基因活跃；而在甜高粱RIO茎秆中蔗糖浓度最高，其蔗糖、淀粉和细胞壁代谢相关基因在茎秆中高表达。渐渗系R9188和其低糖亲本BTx406在开花后蔗糖降解通路相关基因下调，糖磷酸浓度下降，这与淀粉和细胞壁代谢下调一致。研究发现从低糖亲本BTx406渗入到R9188中的多个海藻糖6磷酸调节基因可能与海藻糖6磷酸信号的改变相关，其中包括C族bZIP转录因子和海藻糖6磷酸磷酸酶。在渐渗系R9188中，被逆转的海藻糖6磷酸信号可能参与了下调蔗糖和淀粉代谢，而细胞壁代谢的下调则可能与渗入的多个细胞壁合成、降解基因有关。总而言之，我们的结果展示了在高粱茎秆中不同主要代谢通路的协同作用与甜高粱中的高蔗糖需求和蔗糖积累相关，该研究为遗传改良能源作物中可溶性糖分积累提供了新的候选基因。

通讯：Joachim Messing (https://www.waksman.rutgers.edu/messing/home)

个人简介：德国柏林自由大学，药学学士；慕尼黑路德维希・马西米兰大学，生物化学博士。

研究方向：水稻、高粱、玉米、短柄草等草本植物的基因组测序；谷物种子发育过程中的基因表达调控；甜高粱和浮萍作为生物能源植物的潜在能力。

doi: https://doi.org/10.1111/pbi.12991

Journal: Plant Biotechnology Journal

First Published: 31 July, 2018

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