Effects of 24‐epibrassinolide on freezing and thermotolerance of bromegrass (<i>Bromus inermis</i>) cell cultures

Abstract

The effect of 24‐epibrassinolide (EBS), a brassinosteroid, on the response of smooth bromegrass ( Bromus inermis Leyss) cell suspension cultures under low and high temperature stress was evaluated. EBS minimally increased freezing tolerance of bromegrass cells by 3–5°C, but markedly enhanced cell viability following exposure to high temperature stress. The net effect on hardening was, however, less than that obtained with abscisic acid (ABA). Treatment of cells with EBS increased the accumulation of a subset of ABA‐inducible heat‐stable proteins, but unlike ABA, EBS did not induce the expression of dehydrin transcripts which hybridized to a barley dehydrin clone. EBS slightly increased the hsp90 transcript levels, while ABA reduced the level of expression. These results confirm that brassinosteroids confer some stress tolerance to plant cells and further suggest that the mechanisms by which these compounds exert anti‐stress effects may only in part be similar to that of ABA.