Stress-related genes in woody plants: Transcriptional and posttranscriptional regulation

The induction of gene expression in response to environmental or hormonal cues, has been studied mostly at the of transcriptional level. The importance of post-transcriptional events in determining the final protein levels, however, is now becoming clear. As part of a program to investigate gene expression in woody plants growing under water deficit, we have isolated several cDNA clones of a Proteinase Inhibitor-like gene family from the woody desert shrub, Atriplex canescens. Northern analysis shows a broad inducible signal in response to water deficit. Reverse Transcription-PCR (RT-PCR) experiments show that levels of the individual transcripts are altered to different degrees by exposing plants to water deficit or Abscisic acid. Sequence analysis reveals several motifs in the 3'-untranslated region (3'-UTR) of the mRNA which may contribute to RNA stability or translatability. In a parellel program a cDNA for water deficit-repressible gene is shown to have unusual structure. The longest open reading frame begins over halfway through the mRNA and the 5'-untranslated region (5'-UTR) has extensive secondary structure and several upstream open reading frames (uORFs). These 5'-UTR features are involved in post-transcriptional regulation of gene expression in other eukaryotic systems. Elucildating the function of these sequences will assist in understanding the regulation of stress-inducible genes and in the design of plant transformation vectors to optimize the expression of foreign genes.