Although a considerable amount of circumstantial evidence exists which indicates the involvement of Ca<SUP>2</SUP>&43 in the regulation of phytochrome-mediated responses (Bossen <i>et al</i>., 1988; Viner <i>et al</i>., 1988; Roux, 1986), the exact nature of this involvement has remained unclear. Etiolated wheat leaf protoplasts swell in response to red light (Bossen <i>et al</i>., 1988) by a mechanism which is phytochrome-mediated and is related to leaf growth and unrolling (Zhou <i>et al</i>., 1990). In this study fluorescent Ca<SUP>2</SUP>+ indicators have been used in conjunction with Laser Scanning Confocal Microscopy to measure changes in [Ca<SUP>2</SUP>+ ]<SUB>i</SUB> following red light irradiation of these protoplasts. In most cases (n = 18 of 23), an increase in [Ca<SUP>2</SUP>+ ]<SUB>i</SUB> of approximately 400-700nM was observed, followed by a decrease to below resting level. This response preceded the physiological response of protoplast swelling, although the timing of the [Ca<SUP>2</SUP>+ ]<SUB>i</SUB> response varied between protoplasts. Transient increases in [Ca<SUP>2</SUP>+ ]<SUB>i</SUB> initiated by photoactivation of caged Ca<SUP>2</SUP>+ or caged InsP<SUB>3</SUB> mimicked the swelling response, and photoactivation of Diazo-2, a caged Ca<SUP>2</SUP>+ scavenger, within these protoplasts prevented the swelling response. Data is also presented here which suggests that cAMP, released from caged cAMP, can also induce an increase in protoplast volume, possibly by causing an increase in [Ca<SUP>2</SUP>+ ]<SUB>i</SUB>. These data support the hypothesis that phytochrome signals are transduced through Ca<SUP>2</SUP>+ and suggest a possible role for cAMP in signal transduction within plant cells.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:661759 |
| Date | January 1993 |
| Creators | Shacklock, Philip S. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14380 |
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