Department of Plant Science, University of Tabriz, 51666-16471, Tabriz, Iran.
Department of Plant Science, University of Tabriz, 51666-16471, Tabriz, Iran.
J Trace Elem Med Biol. 2019 Sep;55:96-106. doi: 10.1016/j.jtemb.2019.06.005. Epub 2019 Jun 15.
Leaf senescence is a genetically programmed process that can also be induced by nitrogen (N) deficiency. Although selenium (Se) delays leaf senescence, the underlying mechanisms are still unknown. To explore the mechanisms of Se-mediated delay of leaf senescence, we studied the biochemical and molecular events that occur during developmental and N deficiency-induced senescence. Oilseed rape (Brassica napus L.) plants were grown under adequate N (AN, 16 mM) or low N (LN, 4 mM) conditions during the rosette growth stage and treated with Se (15 μg plant as NaSeO) either through roots or leaves for four weeks. Shoot dry matter production was not influenced, while the photosynthetic parameters were improved by Se application in both young and old leaves under both AN and LN conditions. The Se treatment rarely influenced the concentrations of reactive oxygen species (ROS), while it increased the nitric oxide (NO) levels in young and old leaves under both AN and LN conditions. The positive correlation between the NO level and leaf photosynthetic parameters in old leaves of LN plants suggested a role for NO boosting, mediated by Se, in the protection of aging leaves from LN-induced accelerated senescence. This implication was further supported by the clear down-regulation of SAG12-1 and up-regulation of Cab, particularly by root application of Se in old leaves of LN plants. Our results provide the first evidence that Se influences the expression of senescence-associated genes and delays senescence through NO signalling but is independent of the ROS defence system.
叶片衰老（leaf senescence）是一个由基因编程的过程，也可以被氮（N）缺乏所诱导。尽管硒（Se）可以延缓叶片衰老，但背后的机制仍不清楚。为了探索 Se 介导延缓叶片衰老的机制，我们研究了在发育过程中和 N 缺乏诱导衰老过程中发生的生化和分子事件。在营养生长阶段，将油菜（Brassica napus L.）植株在充足的氮（AN，16mM）或低氮（LN，4mM）条件下培养，并通过根部或叶片用 Se（15μg 植物作为 NaSeO）处理四周。Se 的应用并没有影响 shoot dry matter production，但在 AN 和 LN 条件下，它改善了年轻和老叶片的光合作用参数。Se 处理很少影响活性氧（ROS）的浓度，而在 AN 和 LN 条件下，它增加了年轻和老叶片中的一氧化氮（NO）水平。在 LN 处理的老叶片中，NO 水平与叶片光合参数之间的正相关表明，NO 可能通过 Se 介导，在保护衰老叶片免受 LN 诱导的加速衰老中发挥作用。这一含义进一步得到了证实，即在 LN 处理的老叶片中，通过根部施用 Se，SAG12-1 的明显下调和 Cab 的上调。我们的研究结果首次提供了证据表明，Se 通过 NO 信号影响衰老相关基因的表达并延缓衰老，而这一过程独立于 ROS 防御系统。
