Journal Article

Homologs of Genes Associated with Programmed Cell Death in Animal Cells are Differentially Expressed During Senescence of <i>Ipomoea nil</i> Petals

Tetsuya Yamada, Kazuo Ichimura, Motoki Kanekatsu and Wouter G. van Doorn

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 3, pages 610-625
Published in print March 2009 | ISSN: 0032-0781
Published online January 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp019
Homologs of Genes Associated with Programmed Cell Death in Animal Cells are Differentially Expressed During Senescence of Ipomoea nil Petals

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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In senescent petals of Ipomoea nil, we investigated the expression of genes showing homology to genes involved in animal programmed cell death (PCD). Three encoded proteins were homologous to apoptotic proteins in animals: Bax inhibitor-1 (BI-1), a vacuolar processing enzyme (VPE; homologous to caspases) and a monodehydroascorbate reductase [MDAR; homologous to apoptosis-inducing factor (AIF)]. AIFs harbor an oxidoreductase domain and an apoptotic domain. MDARs exhibit homology to the AIF oxidoreductase domain, not to the apoptotic domain. The three other genes studied relate to autophagy. They encode homologs to vacuolar protein sorting 34 (VPS34) and to the Arabidopsis autophagy-related proteins 4b and 8a (ATG4b and ATG8a). The transcript abundance of MDAR decreased continuously, whereas that of the other genes studies exhibited a transient increase, except ATG4b whose abundance stayed high after an increase. Treatment with ethylene advanced the time to visible petal senescence, and hastened the changes in expression of each of the genes studied. In order to assess the role of VPS34 in petal senescence, we studied the effect of its inhibitor 3-methyladenine (3-MA). 3-MA reduced the time to visible petal senescence, and also accelerated the time to DNA degradation. Remarkably, 3-MA increased the time to nuclear fragmentation, indicating that the time to visible petal senescence was independent of nuclear fragmentation. The data on 3-MA might suggest the idea that autophagy is not a cause of PCD, but part of the remobilization process.

Keywords: Apoptosis; Autophagy; Ethylene; Homologous genes; Petal senescence; Programmed cell death.

Journal Article.  8243 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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