Heat Stress Responses in Cultured Plant Cells

Abstract

The pipetting ofpear (Pyrus communis cv Bartlett) suspension cultures was followed by a substantial but transient decrease in heat sensitivity. During a culture cycle, pear cells were most sensitive to heat at day 3, which coincided with the period of most active cell division. To minimize serious artifacts, the influence of culture handling and age on parameters such as heat sensitivity must be standardized.In the study of complex phenomena such as temperature response, the convenience, simplicity, and uniformity of cell cultures make them valuable experimental systems. Although effects ofheat stress on photosynthesis are critical to whole plants, the absence of chloroplasts in simple cell cultures may further facilitate close examination of other metabolic responses. In considering tissue cultures as model systems, it is important to note that certain aspects of cultured cell response to heat are similar to those of intact plant tissues. Heat stress disrupts polysomes in cells of intact pear fruit (10) and in cultured pear fruit cells (Romani, personal communication). In both intact organs and tissue cultures, heat shock induces acclimation (8,12) and the synthesis of heat-shock proteins (1, 7). However, it is clear that the isolation and culture of plant cells alters physiological characteristics which may influence high temperature response. For example, batch-propagated suspension cultures are characterized by stages ofrelatively high mitotic activity (5). This is relevant to the study of heat stress because certain dividing cells are especially susceptible to heat injury (9, 1 1). Therefore, it is necessary to consider the relationship of culture age to heat sensitivity. Another inherent feature of tissue culture systems is the routine handling and manipulation involved in the transfer and treatment ofcells. Tissue handling has been shown to induce subtle but substantial metabolic changes (13,14), some ofwhich could influence heat tolerance.In this paper, we describe effects of suspension culture age and handling of the heat tolerance of pear cells. (13,14). Our procedure (15) involved pipetting aliquots to test tubes for imposition of heat stress. We found that handling (transfer by pipette) influenced heat sensitivity (Fig. 1)

Heat Stress Responses in Cultured Plant Cells

“…2). As discussed previously (14), the apparent decline in control cell heat tolerance during the 1st d (Fig. 2) probably reflects loss of a transient tolerance induced by culture handling, i.e., return to a normal condition.…”

“…All experiments were conducted with suspension-cultured cells of pear (Pyrus communis cv Bartlett) which were used in our previous studies (13,14). The culture medium and most methods (culture maintenance, growth conditions and measurement, heat stress treatment, and viability tests) were as described before (13).…”

Jasmonic acid is a crucial signal transducer in heat shock induced sesquiterpene formation in Aquilaria sinensis

“…To test this hypothesis, we subjected A. sinensis cell suspension cultures to heat shock treatment, imitating the burn-chisel-drill method utilized on trees, to evaluate the expression levels of genes involved in the JA biosynthesis pathway. As cell suspensions have been reported to exhibit a certain degree of thermo tolerance, cell viability was only affected by temperatures higher than 40 °C; however, cell viability declined significantly at these higher temperatures, and the cells did not exhibit any capacity for growth recovery at temperatures > 50 °C 14 31 32 33 . The heat shock experiment was performed by placing A. sinensis cell suspensions in a 50 °C water bath for 30 min, after which samples were acquired at appointed times for analysis.…”