XVI International Botanical Congess
Growing plants possess many mechanisms for adapting to mild water deficits. Previous work suggested that expansins might be involved in maintenance of cell elongation in drought-stressed maize primary roots (Plant Physiol 111:765). Expansins are wall-loosening proteins thought to be key regulators of wall yielding properties (Plant Physiol 118:333). We have identified maize cDNAs for 14 distinct expansin genes: 6 alpha-expansins and 8 beta-expansins. Five of these expansins are expressed in roots, but none are completely specific to roots. Preliminary results indicate that water stress leads to selective increase in RNA transcripts for one a-expansin and one b-expansin. These results support the hypothesis that drought enhances expression of a subset of the expansin gene family, thereby enabling roots to continue to grow despite low turgor pressure.