Title page for etd-1118111-163748


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URN etd-1118111-163748
Author Zhe-Wei Lin
Author's Email Address No Public.
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Department Biological Sciences
Year 2011
Semester 1
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Characterization of a sweet potato calmodulin that participates in ethephon and salt stress-mediated leaf
Date of Defense 2011-11-17
Page Count 104
Keyword
  • Sweet potato
  • Salt stress
  • Leaf senescence
  • Ethylene
  • Calmodulin
  • Abstract Ethylene is a gaseous growth regulator, and plays an important role in response to plant developmental and environmental stimuli. Ethylene also plays a key role in leaf senescence. Calcium is a second message, and participates in the signal transduction pathways of many plant physiological responses. In this research, ethephon, an ethylene-releasing compound, was used to induce sweet potato leaf yellowing, chlorophyll content reduction, photochemical Fv/Fm decrease, H2O2 elevation and senescence-associated gene expression. These ethephon-mediated effects were all delayed or repressed by pretreatment of a calcium ion chelator, EGTA. Treatment with a calcium ionophore A23187 also induced senescence-associated gene expression in sweet potato detached leaves, and the induction was repressed by EGTA pretreatment. Calcium signaling in general is transmitted by calcium sensor proteins, including calmodulin to translate into appropriate responses to developmental and environmental stimuli. Therefore, pretreatment with calmodulin inhibitor chlorpromazine (CPZ) delayed or repressed ethephon-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression. These CPZ-mediated effects were reversed by the exogenous application of an ethephon-inducible calmodulin SPCAM fusion protein. These results suggest that external Ca2+ influx and calmodulin SPCAM play a role in ethephon signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression. In addition, NaCl salt stress also caused sweet potato leaf senescence, H2O2 elevation and senescence-associated gene expression. Pretreatment with CPZ delayed or repressed NaCl salt stress-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression. These CPZ-mediated effects were also reversed by the exogenous application of calmodulin SPCAM fusion protein. These results suggest that calmodulin SPCAM may play a role in NaCl salt stress signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression. Based on these results, external Ca2+ influx is required for ethephon induced leaf senescence. Ethephon-inducible calmodulin SPCAM likely participates in ethylene and NaCl salt stress signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression in sweet potato in order to cope with different developmental cues or environmental stimuli.
    Advisory Committee
  • Liu, Zin-Huang - chair
  • Tse-Min Lee - co-chair
  • Chen, Hsien-Jung - advisor
  • Files
  • etd-1118111-163748.pdf
  • Indicate in-campus at 5 year and off-campus access at 5 year.
    Date of Submission 2011-11-18

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