PubMed · 3205138
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I A Balandina. 1988. [Buckwheat].. https://pubmed.ncbi.nlm.nih.gov/3205138/
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Tolerance to dehydration induced by repeated water-deficit stress is well correlated to changes in the lipid composition of oat root cell plasma membranes. The molecular species of the two dominant phospholipids phosphatidylcholine and phosphatidylethanolamine were determined. The four major species were 16:0/18:2, 16:0/18:3, 18:2/18:2 and 18:2/18:3. In contrast to the large changes in plasma membrane lipid composition in other respects, induced tolerance resulted in very weak alterations concerning the phospholipid molecular species pattern. Only minor alterations, appearing as a decrease in the 18:3-containing lipids, occurred. Total lipids of microsomes and isolated plasma membranes of root cells were analysed by X-ray crystallography at different degrees of hydration. The lipid phase behaviour at different degrees of hydration was further confirmed by polarization microscopy. In the presence of excess water all membrane lipids adopted a reversed micellar configuration. The plasma membrane lipids from root cells with induced dehydration tolerance formed upon dehydration two coexisting lamellar structures. The importance of the phase behaviour at different degrees of hydration for the membrane properties and the relation to membrane composition is discussed.
Phytochrome is the ubiquitous red light photoreceptor present in plants. Properties of the 6-kDa end terminal region of phytochrome A (PHYA from etiolated Avena) have been investigated by the use of synthetic polypeptide fragments corresponding to that region. This region of the phytochrome A protein has been viewed as a possible functional site due to the large differences in the sequence's conformation and exposure between the Pr (red light-absorbing form) and Pfr (far-red light-absorbing, gene-regulating form) species of phytochrome A. Hydrophobic moment calculations reveal amphiphilic helical potential in this section of the protein, consistent with the folding of the N-terminal region onto a hydrophobic chromophore/chromophore pocket. A large N-terminal synthetic peptide also demonstrated helical folding in the presence of SDS micelles. This experimental evidence indicates that the N-terminal alpha-helical folding upon conversion of the regulatorily inactive Pr to the active Pfr form of phytochrome A is likely driven at least in part by amphiphilic helix stabilization. Further, the large synthetic peptide was spectrally demonstrated to interact with phytochrome A lacking the N-terminal region. The formation of this nativelike complex may provide us with a tool for both biophysical and physiological studies on the mechanism of phytochrome A signal transduction.
The value of taxonomy lies in its ability to communicate concepts and relationships. Our present concepts of the poaceous potyviruses, based on their biology, serology, and biochemistry, identify four viruses that can be distinguished by each characteristic. Identifying these as four distinct viruses has important implications for disciplines such as epidemiology, plant breeding, and diagnostics.