NARO Institute of Floricultural Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Japan.
J Exp Bot. 2013 Feb;64(4):1111-20. doi: 10.1093/jxb/ers395. Epub 2013 Jan 23.
Autophagy is one of the main mechanisms of degradation and remobilization of macromolecules, and it appears to play an important role in petal senescence. However, little is known about the regulatory mechanisms of autophagy in petal senescence. Autophagic processes were observed by electron microscopy and monodansylcadaverine staining of senescing petals of petunia (Petunia hybrida); autophagy-related gene 8 (ATG8) homologues were isolated from petunia and the regulation of expression was analysed. Nutrient remobilization was also examined during pollination-induced petal senescence. Active autophagic processes were observed in the mesophyll cells of senescing petunia petals. Pollination induced the expression of PhATG8 homologues and was accompanied by an increase in ethylene production. Ethylene inhibitor treatment in pollinated flowers delayed the induction of PhATG8 homologues, and ethylene treatment rapidly upregulated PhATG8 homologues in petunia petals. Dry weight and nitrogen content were decreased in the petals and increased in the ovaries after pollination in detached flowers. These results indicated that pollination induces autophagy and that ethylene is a key regulator of autophagy in petal senescence of petunia. The data also demonstrated the translocation of nutrients from the petals to the ovaries during pollination-induced petal senescence.
自噬是生物大分子降解和再循环的主要机制之一，它在花瓣衰老过程中似乎起着重要作用。然而，关于自噬在花瓣衰老中的调控机制知之甚少。通过电镜和对衰老的矮牵牛花瓣中单丹磺酰尸胺染色观察到自噬过程；从小矮牵牛中分离出自噬相关基因 8 (ATG8) 同源物，并分析了其表达的调控。在授粉诱导的花瓣衰老过程中也检查了营养物质的再循环。在衰老的矮牵牛花瓣的叶肉细胞中观察到活跃的自噬过程。授粉诱导 PhATG8 同源物的表达，并伴随着乙烯生成的增加。在授粉的花朵中用乙烯抑制剂处理会延迟 PhATG8 同源物的诱导，而乙烯处理会迅速上调矮牵牛花瓣中的 PhATG8 同源物。在离体花朵授粉后，花瓣中的干重和氮含量下降，而子房中的干重和氮含量增加。这些结果表明授粉诱导自噬，而乙烯是矮牵牛花瓣衰老中自噬的关键调节因子。这些数据还表明，在授粉诱导的花瓣衰老过程中，营养物质从花瓣向子房转移。
