Pollination induces autophagy in petunia petals via ethylene.
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.
NARO Institute of Floricultural Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Japan. shibuken@affrc.go.jp
Kenichi
K
Shibuya
Tomoko
T
Niki
Kazuo
K
Ichimura
D001343:Autophagy; D001692:Biological Transport; D002103:Cadaverine / Q000031:analogs & derivatives / Q000378:metabolism; D005030:Ethylenes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D035264:Flowers / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D058503:Mesophyll Cells / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D005810:Multigene Family; D032306:Petunia / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism*; D059828:Plant Cells / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D054817:Pollination; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D005030:Ethylenes; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; C036216:ethylene; C008542:monodansylcadaverine; D002103:Cadaverine