Photoperiod Extension Enhances Sexual Megaspore Formation and Triggers Metabolic Reprogramming in Facultative Apomictic Ranunculus auricomus.
Photoperiod Extension Enhances Sexual Megaspore Formation and Triggers Metabolic Reprogramming in Facultative Apomictic Ranunculus auricomus.
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DOI：
10.3389/fpls.2016.00278
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发表时间：
2016
影响因子：
5.6
通讯作者：
Hörandl E
中科院分区：
文献类型：
--
作者：
Klatt S;Hadacek F;Hodač L;Brinkmann G;Eilerts M;Hojsgaard D;Hörandl E
减数分裂是有性生殖的关键步骤，在兼性无融合生殖植物中持续存在，并在一定程度上发挥功能。然而，目前仍不清楚生殖途径的比例在不同环境胁迫条件下如何以及为何变化。我们假设氧化应激介导发育途径的改变。在无融合生殖植物中，我们预计大孢子发生（减数分裂后的直接阶段）将比种子发育的后期阶段受到更大的影响。为了模拟中等压力条件，我们将兼性无融合生殖毛茛属 auricomus 的克隆交配置于 10 小时的光周期（反映自然条件）和延长的光周期（16.5 小时）下。在大孢子发生后（显微镜）和种子阶段（流式细胞术种子筛选）直接筛选繁殖模式。使用 HPLC-DAD 进行目标代谢物分析，以探索是否以及哪些代谢重编程是由延长的光周期引起的。延长的光周期导致减数分裂后有性与无性生殖初始频率的增加，但不影响有性与无性种子形成的频率。延长光周期下次级代谢产物谱的变化影响所有类别的化合物，c．其中 20% 的变化将两种治疗方法区分开来。出乎意料的是，著名的抗氧化剂苯丙素和黄酮类化合物对克隆交配变异的作用比对治疗分化的作用更大。其中，叶绿素降解产物、未指定的酚类化合物和更多亲脂性代谢物也导致暴露于两种不同光周期的植物代谢谱的不同。有性大孢子发育比例的增加以无孢子初始形成为代价，支持了中度光胁迫效应的假说。种子阶段缺乏影响证实了只有减数分裂和孢子发生对光胁迫敏感的基本假设。作为早期发育阶段的系统反应，次生代谢物谱的伴随变化支持了氧化应激可能通过引起观察到的代谢重编程影响大孢子发生的观点。基因型特异性对延长光周期反应的假设被拒绝。
Meiosis, the key step of sexual reproduction, persists in facultative apomictic plants functional to some extent. However, it still remains unclear how and why proportions of reproductive pathways vary under different environmental stress conditions. We hypothesized that oxidative stress mediates alterations of developmental pathways. In apomictic plants we expected that megasporogenesis, the stage directly after meiosis, would be more affected than later stages of seed development. To simulate moderate stress conditions we subjected clone-mates of facultative apomictic Ranunculus auricomus to 10 h photoperiods, reflecting natural conditions, and extended ones (16.5 h). Reproduction mode was screened directly after megasporogenesis (microscope) and at seed stage (flow cytometric seed screening). Targeted metabolite profiles were performed with HPLC–DAD to explore if and which metabolic reprogramming was caused by the extended photoperiod. Prolonged photoperiods resulted in increased frequencies of sexual vs. aposporous initials directly after meiosis, but did not affect frequencies of sexual vs. asexual seed formation. Changes in secondary metabolite profiles under extended photoperiods affected all classes of compounds, and c. 20% of these changes separated the two treatments. Unexpectedly, the renowned antioxidant phenylpropanoids and flavonoids added more to clone-mate variation than to treatment differentiation. Among others, chlorophyll degradation products, non-assigned phenolic compounds and more lipophilic metabolites also contributed to the dissimilarity of the metabolic profiles of plants that had been exposed to the two different photoperiods. The hypothesis of moderate light stress effects was supported by increased proportions of sexual megaspore development at the expense of aposporous initial formation. The lack of effects at the seed stage confirms the basic assumption that only meiosis and sporogenesis would be sensitive to light stress. The concomitant change of secondary metabolite profiles, as a systemic response at this early developmental stage, supports the notion that oxidative stress could have affected megasporogenesis by causing the observed metabolic reprogramming. Hypotheses of genotype-specific responses to prolonged photoperiods are rejected.