Integrative analysis of the einkorn (Triticum monococum) grain reveals new mechanisms of response to sulfur deficiency

In wheat, the main staple crop in many regions of the word, one major challenge is to improve the yield potential while maintaining the grain quality, which is mainly defined by its protein concentration and composition. To achieve this goal, it is essential to considerate the nitrogen (N) and sulfur (S) nutrition, which strongly influences the grain storage protein (GSP) composition. Nowadays, the limitation of nitrogen inputs and the sulfur deficiency recently observed in soils represent major difficulties to control the grain quality. Thus, identification of the molecular mechanisms that control the accumulation of GSP in response to N and S supply is necessary. In this study, we applied four post-anthesis N and S treatments to an einkorn (Triticum monococcum) culture. Effects of the treatments on the grain transcriptome and metabolome were evaluated at different times during grain development. From the 386 differentially expressed genes and the 21 metabolites differentially accumulated, our results have revealed a strong impact of a high-N supply without any added S. A large majority of genes were transiently influenced by the treatments while others showed strong modifications of their kinetics of expression during grain filling. We hypothesized the role of several genes (e.ge.g. sulfate transporters, transcriptional regulators) in the adjustment of the N-to-S ratio in response to a S deficiency. These genes could coordinate the amino acid pool necessary for GSP synthesis. These new results contribute in facing the challenge of maintaining wheat grain quality for the development of more sustainable agriculture. Transcriptome comparisons between four N and S treatments and between six grain develomental stages in three replicates

作为全球众多地区的主粮作物，小麦面临的核心挑战之一，是在提升产量潜力的同时维持籽粒品质——籽粒品质主要由其蛋白质浓度与组成决定。为达成这一目标，必须考量氮（Nitrogen, N）与硫（Sulfur, S）营养状况，二者对籽粒贮藏蛋白（Grain Storage Protein, GSP）的组成具有显著调控作用。当下，氮肥投入受限与近期在土壤中观测到的硫素缺乏，已成为调控籽粒品质的主要阻碍。因此，解析响应氮、硫供给的籽粒贮藏蛋白积累分子机制，成为亟需开展的研究工作。本研究针对一粒小麦（Triticum monococcum）种植体系，设置了4种花后氮、硫处理组合。我们在籽粒发育的不同阶段，评估了上述处理对籽粒转录组与代谢组的影响。通过对386个差异表达基因与21个差异积累代谢物的分析，本研究结果揭示了无额外硫供给的高氮处理所产生的显著调控效应。绝大多数基因仅受处理的瞬时调控，另有部分基因在籽粒灌浆过程中表现出表达动力学的显著改变。我们推测，若干基因（例如硫酸盐转运蛋白、转录调控因子）在响应硫素缺乏的氮硫比调控过程中发挥关键作用。这类基因可协同调控籽粒贮藏蛋白合成所需的氨基酸池。本研究的新发现，可为应对可持续农业发展中维持小麦籽粒品质的挑战提供重要支撑。本研究设置3次生物学重复，对4种氮、硫处理组合及6个籽粒发育阶段的转录组开展了比较分析。