Developmental and stress regulation of RCI2A and RCI2B, two cold-induciblegenes of arabidopsis encoding highly conserved hydrophobic proteins

The capability of most higher plants to tolerate environmental conditions s trongly depends on their developmental stage. In addition, environmental fa ctors have pleiotropic effects on many developmental processes. The interac tion between plant development and environmental conditions implies that so me genes must be regulated by both environmental factors and developmental cues. To understand their developmental regulation and obtain possible clue s on their functions, we have isolated genomic clones for RCI2A and RCI2B, two genes from Arabidopsis ecotype Columbia (Col), whose expression is indu ced in response to low temperature, dehydration, salt stress, and abscisic acid. The promoters of RCI2A and RCI2B were fused to the uidA (GUS)-coding sequence and the resulting constructs used to transform Arabidopsis. GUS ac tivity was analyzed in transgenic plants during development under both stre ssed and unstressed conditions. Transgenic plants with either the RCI2A or RCI2B promoter showed strong GUS expression during the first stages of seed development and germination, in vascular bundles, pollen, and most interes tingly in guard cells. When transgenic plants were exposed to low temperatu re, dehydration, salt stress, or abscisic acid, reporter gene expression wa s induced in most tissues. These results indicate that RCI2A and RCI2B are regulated at transcriptional level during plant development and in response to different environmental stimuli and treatments. The potential role of R CI2A and XCI2B in plant development and stress response is discussed.