The New Zealand Institute for Plant Food Research Limited, Private Bag 11600, Palmerston North 4442, New Zealand.
Plant Physiol. 2012 Nov;160(3):1357-72. doi: 10.1104/pp.112.203083. Epub 2012 Aug 28.
Senescence is genetically controlled and activated in mature tissues during aging. However, immature plant tissues also display senescence-like symptoms when continuously exposed to adverse energy-depleting conditions. We used detached dark-held immature inflorescences of Arabidopsis (Arabidopsis thaliana) to understand the metabolic reprogramming occurring in immature tissues transitioning from rapid growth to precocious senescence. Macroscopic growth of the detached inflorescences rapidly ceased upon placement in water in the dark at 21°C. Inflorescences were completely degreened by 120 h of dark incubation and by 24 h had already lost 24% of their chlorophyll and 34% of their protein content. Comparative transcriptome profiling at 24 h revealed that inflorescence response at 24 h had a large carbon-deprivation component. Genes that positively regulate developmental senescence (ARABIDOPSIS NAC DOMAIN CONTAINING PROTEIN92) and shade-avoidance syndrome (PHYTOCHROME INTERACTING FACTOR4 [PIF4] and PIF5) were up-regulated within 24 h. Mutations in these genes delayed degreening of the inflorescences. Their up-regulation was suppressed in dark-held inflorescences by glucose treatment, which promoted macroscopic growth and development and inhibited degreening of the inflorescences. Detached inflorescences held in the dark for 4 d were still able to reinitiate development to produce siliques upon being brought out to the light, indicating that the transcriptional reprogramming at 24 h was adaptive and reversible. Our results suggest that the response of detached immature tissues to dark storage involves interactions between carbohydrate status sensing and light deprivation signaling and that the dark-adaptive response of the tissues appears to utilize some of the same key regulators as developmental senescence.
衰老在成熟组织中受到遗传控制，并在衰老过程中被激活。然而，当不成熟的植物组织持续暴露在消耗能量的不利条件下时，也会表现出类似衰老的症状。我们使用拟南芥（Arabidopsis thaliana）的离体黑暗保持的未成熟花序来理解在从快速生长到早熟衰老的转变过程中，不成熟组织中发生的代谢重编程。在 21°C 的黑暗中，将离体花序放置在水中后，其宏观生长迅速停止。黑暗培养 120 小时后，花序完全褪绿，24 小时后，已损失 24%的叶绿素和 34%的蛋白质含量。24 小时的比较转录组分析显示，花序在 24 小时的反应具有较大的碳剥夺成分。正向调节发育性衰老的基因（ARABIDOPSIS NAC DOMAIN CONTAINING PROTEIN92）和遮荫避免综合征（PHYTOCHROME INTERACTING FACTOR4 [PIF4] 和 PIF5）在 24 小时内被上调。这些基因的突变延迟了花序的褪绿。在黑暗保持的花序中，葡萄糖处理抑制了它们的上调，葡萄糖处理促进了宏观生长和发育，抑制了花序的褪绿。在黑暗中保持 4 天的离体花序在被带到光下后仍能重新开始发育，产生蒴果，这表明 24 小时的转录重编程是适应性和可逆的。我们的结果表明，离体未成熟组织对黑暗储存的反应涉及碳水化合物状态感知和光剥夺信号之间的相互作用，并且组织的黑暗适应反应似乎利用了一些与发育性衰老相同的关键调节因子。
