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Association of Phytochrome with Rough-surfaced Endoplasmic Reticulum Fractions from Soybean Hypocotyls
1Departments of Botany and Plant Pathology and Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Phytochrome distribution in soybean hypocotyls shows most is soluble. Membrane-bound phytochrome, particularly with Mg(2+), associates with rough endoplasmic reticulum, but contamination cannot be ruled out.
Area of Science:
- Plant biology
- Molecular biology
- Cell biology
Background:
- Phytochrome, a plant photoreceptor, plays a crucial role in light-mediated development.
- Understanding phytochrome's localization within plant cells is key to elucidating its signaling mechanisms.
Purpose of the Study:
- To determine the distribution of active phytochrome (Pfr) among cellular membranes in soybean hypocotyls.
- To investigate the influence of magnesium ions (Mg2+) on phytochrome-membrane association.
Main Methods:
- Cell fractionation to isolate cellular components.
- Difference spectrometry to quantify phytochrome.
- Electron microscopic morphometry for ultrastructural analysis.
Main Results:
- Over 90% of phytochrome was found in the soluble fraction.
- Membrane-associated phytochrome was low (6.5% with Mg2+, 1% without).
- With Mg2+, phytochrome correlated with rough endoplasmic reticulum; without Mg2+, it associated with plasma membranes, possibly due to ER contamination.
Conclusions:
- Phytochrome primarily exists in the soluble fraction of soybean hypocotyl cells.
- While phytochrome shows association with rough endoplasmic reticulum in the presence of Mg2+, this could be due to co-sedimentation with contaminating ER fragments.
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