CELL-WALL PROTEINS INDUCED BY WATER-DEFICIT IN BEAN (PHASEOLUS-VULGARIS L) SEEDLINGS

In the last few years, much attention has been given to the role of proteins that accumulate during water deficit. In this work, we analyzed the electrophoretic patterns of basic protein extracts, enriched for a number of cell-wall proteins, from bean (Phaseolus vulgaris L.) seedlings and 21-d-old plants subjected to water deficit. Three major basic proteins accumulated in bean seedlings exposed to low water potentials, with apparent molecular masses of 36, 33, and 22 kD, which we refer to as p36, p33, and p22, respectively. Leaves and roots of 21-d-old plants grown under low-water-availability conditions accumulated only p36 and p33 proteins. In 21-d-old plants subjected to a fast rate of water loss, both p33 and p36 accumulated to approximately the same levels, whereas if the plants were subjected to a gradual loss of water, p33 accumulated to higher levels. Both p36 and p33 were glycosylated and were found in the cell-wall fraction. In contrast, p22 was not glycosylated and was found in the soluble fraction. The accumulation of these proteins was also induced by abscisic acid (0.1-1.0 mM) treatment but not by wounding or by jasmonate treatment.