College of Agro-Grassland Science, Nanjing Agricultural University, Nanjing, China.
Department of Plant Biology, Rutgers University, New Brunswick, New Jersey, USA.
Physiol Plant. 2021 Dec;173(4):1979-1991. doi: 10.1111/ppl.13541. Epub 2021 Sep 8.
The nonyellow COLORING 1-like gene (NOL) is known for its roles in accelerating leaf senescence, but the underlying metabolic mechanisms for heat-induced leaf senescence remain unclear. The objectives of this study were to identify metabolites and associated metabolic pathways regulated by knockdown of NOL in perennial ryegrass (Lolium perenne) and to determine the metabolic mechanisms of NOL controlling heat-induced leaf senescence. Wild-type (WT; cv. "Pinnacle") and two lines (Noli-1 and Noli-2) of perennial ryegrass with LpNOL knockdown were exposed to heat stress at 35/33°C (day/night) or nonstress control temperatures at 25/22°C (day/night) for 30 days in growth chambers. Leaf electrolyte leakage, chlorophyll (Chl) content, photochemical efficiency (F /F ), and net photosynthetic rate (Pn) were measured as physiological indicators of leaf senescence, while gas chromatography-mass spectrometry was performed to identify metabolites regulated by LpNOL. Knockdown of LpNOL suppressed heat-induced leaf senescence and produced a stay-green phenotype in perennial ryegrass, as manifested by increased Chl content, photochemical efficiency, net photosynthetic rate, and cell membrane stability in Noli-1 and Noli-2. Five metabolites (valine, malic acid, threonic acid, shikimic acid, chlorogenic acid) were uniquely upregulated in LpNOL plants exposed to heat stress, and six metabolites (aspartic acid, glutamic acid, 5-oxoproline, phenylalanine, proline, tartaric acid) exhibited more pronounced increases in their content in LpNOL plants than the WT. LpNOL could regulate heat-induced leaf senescence in perennial ryegrass through metabolic reprogramming in the pathways of respiration, secondary metabolism, antioxidant metabolism, and protein synthesis.
非黄色素 1 样基因（NOL）因其在加速叶片衰老中的作用而闻名，但热诱导叶片衰老的潜在代谢机制仍不清楚。本研究的目的是鉴定多年生黑麦草（Lolium perenne）中 NOL 敲低调控的代谢物及其相关代谢途径，并确定 NOL 控制热诱导叶片衰老的代谢机制。在生长室中，将野生型（WT；品系“Pinnacle”）和两种具有 LpNOL 敲低的多年生黑麦草品系（Noli-1 和 Noli-2）在 35/33°C（白天/夜晚）或非胁迫对照温度 25/22°C（白天/夜晚）下分别暴露于热胁迫 30 天。用电导率仪法测定叶片电解质渗透率，叶绿素（Chl）含量，光化学效率（F / F m）和净光合速率（Pn）作为叶片衰老的生理指标，同时采用气相色谱-质谱联用技术（GC-MS）鉴定受 LpNOL 调控的代谢物。LpNOL 敲低抑制了多年生黑麦草的热诱导叶片衰老，产生了“持绿”表型，表现在 Noli-1 和 Noli-2 中的 Chl 含量、光化学效率、净光合速率和细胞膜稳定性增加。在 LpNOL 植株中，有 5 种代谢物（缬氨酸、苹果酸、苏糖酸、莽草酸、绿原酸）在热胁迫下被特异性地上调，有 6 种代谢物（天冬氨酸、谷氨酸、5-氧脯氨酸、苯丙氨酸、脯氨酸、酒石酸）在 LpNOL 植株中的含量比 WT 更为显著增加。LpNOL 可能通过呼吸作用、次生代谢、抗氧化代谢和蛋白质合成途径的代谢重编程来调节多年生黑麦草的热诱导叶片衰老。
