Molecular biology of the plasma membrane of higher plants.

In plants, as in all organisms, the plasma membrane serves two main roles: (1) the transport of solutes, both into and out of each cell, and (2) sensory transduction, i.e., the sensing and initiation of the cellular response to changing environmental conditions. Recently, considerable progress has been made in elucidating the role of specific plasma membrane proteins in these two processes. Historically, in all eukaryotes, this research area was hampered by problems in membrane purification as well as by difficulties in the purification and sequencing of water-insoluble membrane proteins. lncreased ease in DNA cloning and sequencing procedures, as well as improvements in detergent-based chromatography techniques, have alleviated some of these problems. Thus, although the plasma membrane has been the subject of physiological and biochemical research for severa1 decades, only recently has the molecular analysis of plasma membrane proteins been achieved. This past year the first genes encoding plant plasma membrane proteins were cloned and sequenced. In reports from two separate laboratories, three genes encoding plasma membrane proton pumps (H’-ATPases) from Arabidopsis thaliana were described (Harper, Surowy, and Sussman, 1989; Pardo and Serrano, 1989), and a third laboratory has recently described genes encoding this enzyme from tobacco (Nicotiana plumbaginifolia) (Boutry, Michelet, and Goffeau, 1989). As of this writing there are two other preliminary reports on cloning plasma membrane protein genes from higher plants: ATPase genes from tomato (Bennett, Ewing, and Wimmers, 1989) and Gprotein genes from corn (Palme et al., 1989). This review will focus on recent findings concerning the genomic and cDNA structure of genes encoding the plasma membrane proton pump from higher plants and relate them to pumps from other organisms. In addition, we will present a list of other known plant plasma membrane proteins and discuss future strategies for cloning their genes. For additional general reviews on the plasma membrane proton pump,