Science：植物区分不同的光周期以独立控制季节性开花和生长（耶鲁大学）

这是郝事之秋陪你的第2179天！

Hope everybody can study well and make progress every day!

第一作者

：Qingqing Wang

第一单位

：耶鲁大学

通讯作者

：Joshua M. Gendron

Abstract

背景回顾：Daylength, or photoperiod, is a stable indicator of the season, and organisms can measure photoperiods to predict seasonal changes in climate. In plants, flowering and growth are often regulated by photoperiod, and the photoperiodic flowering pathway is well understood. By contrast, much less is known about how photoperiod regulates growth, including the measurement system and genes that are required. 

基本原理：Studies of photoperiodic flowering have benefitted from mutants with obvious defects in seasonal flowering time, and genes whose expression is controlled by photoperiod and can be tracked under different daylengths. We hypothesized that similar tools would allow for increased understanding of the genes and measurement systems that participate in photoperiodic growth, potentially revealing a different mechanism than is used for seasonal flowering. 

结果1-关键基因MIPS1：Arabidopsis thaliana grows faster in long days, so we mined transcriptomic data for genes that are induced in long days and required for proper vegetative growth. We identified MYO-INOSITOL-1-PHOSPHATE SYNTHASE 1 (MIPS1), which encodes a gene necessary for plants to produce myo-inositol, a sugar required for a variety of important cellular processes that control growth. We then showed that MIPS1 expression is induced during long but not short days and that a mips1 mutant plant has growth defects in long but not short days. 

结果2-光周期开花和生长相互独立：Because the flowering photoperiod measurement system has been characterized in plants, we tested whether our growth mutants were in the same pathway. We found that the mips1 mutant has no flowering defect, and photoperiodic flowering mutants have no growth defect, results that were confirmed by double mutants with mips1 and photoperiodic flowering mutantions. These experiments showed that photoperiodic flowering and growth are genetically separable and that the photoperiod measurement system governing flowering is not controlling photoperiodic growth. 

结果3-光周期开花和生长测量的并非同一个光周期：Further experiments showed that MIPS1 expression and function are regulated by a circadian clock–controlled metabolic daylength measurement system. By changing light intensities over the course of a day while maintaining the integrated intensity, we demonstrated that photoperiodic growth and MIPS1 function are controlled by the photosynthetic period and that flowering is controlled by a wholly different photoperiod. 

结论：Our results show that plants can measure two different photoperiods in natural day cycles. They can detect an absolute photoperiod with low light–detecting photoreceptor systems to control flowering time. In parallel, they can measure the photosynthetic period as a metabolic daylength to control growth. This allows plants to independently coordinate seasonal developmental processes. This work opens the possibility that several photoperiod measurement systems can operate in parallel in organisms to precisely regulate a variety of seasonal processes.

摘 要

日长，或者叫光周期，是季节的一个稳定指示器，生物能够通过测量光周期来预测气候的季节变化。在植物中，开花和生长通常受到光周期的调控，并且光周期开花途径的研究也比较透彻了。相反，对于光周期如何调控生长的却所知不多，包括光周期测量系统以及需要哪些个基因，这些都不清楚。对于在季节性开花时间方面存在明显缺陷表型的突变体鉴定，促进了我们对于光周期开花的研究。那些表达量受到光周期控制的基因，可以在不同的日常条件下追踪到其表达变化。作者假设，类似的方法也可以用来研究参与光周期生长相关的基因及测量系统，从而揭示一个不同于季节性开花的分子机制。拟南芥在长日照条件下生长更快，所以作者挖掘了受长日照诱导表达且对于正确营养生长必需的转录组数据。作者鉴定到了一个叫做MIPS1的基因，该基因在植物中作用于肌醇的合成，而肌醇是一种控制生长的各种重要细胞过程所需要的糖。接着，作者发现MIPS1的表达受到长日照的诱导，但是短日照不行。另外，mips1突变体在长日照条件下生长出现缺陷，但在短日照条件下不会。因为植物中开花光周期测量系统已经很明确了，作者测试了mips1突变体是否也在同一个通路中。作者发现mips1突变体没有任何开花缺陷，同时光周期开花突变体也不存在任何生长缺陷。这些试验结果表明，开花和生长在遗传上是分离的，光周期测量系统作用于光周期开花，但是并不会控制光周期生长。进一步的研究显示，MIPS1基因的表达和功能受到一个生物钟控制的代谢日长测量系统的调控。通过保持累计强度的不变而改变一天中的光照强度，作者发现光周期生长和MIPS1功能受到光周期的调控，但是开花受到一个完全不同的光周期控制。作者的结果显示，植物能够在自然日周期中测量两种不同的光周期。植物可以利用弱光检测光受体系统来检测绝对光周期，从而控制开花时间。同时，植物还可以通过代谢日长来测量光周期，从而控制生长。这使得植物能够完全独立的协调季节性发育过程。本文的工作开启了一种可能性，即几种光周期测量系统可以在生物体内平行运转，从而实现对多个季节性过程的精确调节。

END