Light, temperature and circadian clock signal integration during leaf senescence

叶片衰老是一个活跃的过程，包括将营养物质从较老的、受光合作用限制的组织重新动员到正在发育的植物结构中。它的特征是由于叶绿体的分解和叶绿素的降解而导致叶片显着变黄。叶片衰老可由环境胁迫引起，如长时间的黑暗，并在高温下加速衰老。在商业园艺中，切花产品中的叶片衰老降低了作物的品质和货架期，给种植者造成了巨大的经济损失。由于农产品在温暖和黑暗的条件下运输和储存，这一问题变得更加严重，这要求生产商和零售商投资于昂贵且不环保的制冷技术。可持续地延缓叶片衰老是生鲜食品行业的一个关键目标，但成本效益高、实用的解决方案仍然有限。在模式植物拟南芥中，暗诱导的叶片衰老受到光、温度和昼夜时钟调节的转录因子、光敏色素相互作用因子4(PIF4)和PIF5的促进。Franklin实验室已经证明，低剂量(非胁迫)UV-B光处理可以促进PIF4和PIF5蛋白的快速降解，并抑制PIF4和PIF5基因的表达。UV-B在商业温室中由玻璃过滤，不是垂直农场园艺照明的组成部分。因此，在商业园艺中使用的大多数受保护的种植环境中都没有紫外线-B。我们有初步证据表明，在采收前进行短时间(4小时)的低剂量UV-B处理可以显著减少在较高温度下储存的拟南芥离体叶和子叶中暗诱导的衰老。这种处理抑制了关键的衰老调节因子OR1的表达，并延缓了叶绿素的降解。这项拟议的工作将剖析光、温度和昼夜节律时钟控制暗诱导的拟南芥叶片衰老的分子信号通路。除了进一步从机制上深入了解关键发育过程的调控，这项工作还将为利用采前和采后光处理延缓作物暗诱导的叶片衰老提供策略。我们的初步数据表明，采收前的UV-B处理可以延缓暗诱导的火箭(Eruca Sativa)幼叶衰老，支持我们的方法。总体而言，拟议的工作将提供一个分子框架，以解决可持续食品储存中的一个关键问题。

Leaf senescence is an active process involving the remobilisation of nutrients from older, photosynthetically limited tissues to developing plant structures. It is characterised by striking leaf yellowing resulting from the dismantling of chloroplasts and degradation of chlorophyll. Leaf senescence can be induced by environmental stress, such as prolonged darkness and is accelerated at high temperature. In commercial horticulture, leaf senescence in cut produce reduces crop quality and shelf-life, resulting in significant economic losses to growers. This problem is exacerbated by the transport and storage of produce in warm and dark conditions, requiring producers and retailers to invest in costly and environmentally unfriendly refrigeration technologies. Sustainably delaying leaf senescence is a key objective for the fresh food industry, yet cost-effective, practical solutions remain limited. In the model plant Arabidopsis thaliana, dark- induced leaf senescence is promoted by the light, temperature and circadian clock-regulated transcription factors, PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5. The Franklin lab has shown that low dose (non-stressful) UV-B light treatment can promote rapid degradation of PIF4 and PIF5 proteins and suppress the expression of PIF4 and PIF5 genes in Arabidopsis seedlings. UV-B is filtered by glass in commercial greenhouses and is not a component of horticultural lighting in vertical farms. As such, UV-B is absent in the majority of protected growing environments used in commercial horticulture. We have preliminary evidence that a short (4 hour) preharvest treatment of low dose UV-B can significantly reduce dark-induced senescence in detached Arabidopsis leaves and cotyledons stored at warmer temperatures. This treatment supresses the expression of the key senescence regulator, ORE1 and delays chlorophyll degradation. The proposed work will dissect the molecular signalling pathways through which light, temperature and the circadian clock control dark-induced senescence in detached Arabidopsis leaves. In addition to furthering mechanistic insight into the regulation of a key developmental process, the work will inform strategies for using pre and postharvest light treatments to delay dark-induced leaf senescence in crops. Our preliminary data suggest that preharvest UV-B treatment can delay dark-induced senescence in young rocket (Eruca sativa) leaves, supporting our approach. Overall, the proposed work will provide a molecular framework to address a key problem in sustainable food storage.