Changes in gene expression induced by water stress in tomato.

摘要

Drought limits plant growth more than any other single environmental factor. The identification of gene products that accumulate in plants after the onset of water stress is the principal goal of this study. Poly(A) RNA from control and stressed tomato leaves was translated in vitro and the translation products resolved by two-dimensional gel electrophoresis. The level of several mRNAs was found to increase in detached stressed leaves and in leaves from intact plants stressed in situ.; A cDNA library was generated from poly(A) RNA isolated from leaves that were stressed for 2 hrs after being detached. The library was screened by differential hybridization using {dollar}sp{lcub}32{rcub}{dollar}P-labelled cDNA prepared from poly (A) RNA of both control and stressed leaves. A clone that preferentially hybridized to cDNA prepared from stressed leaves was selected. This clone, pLE25, hybridized to an RNA species of about 1 kb present in the stressed but not in the control sample. The sequence of pLE25 was determined and found to contain an open reading frame encoding a protein of 229 amino acid residues and a 3{dollar}spprime{dollar}nontranslated region of 175 base pairs. The polypeptide deduced from the nucleotide sequence has a molecular weight of 24,910 daltons, contains high levels of glycine (15%) and displays a hydrophilic character of hydropathy plots.; The mRNA corresponding to pLE25 can be detected within 20 min of the onset of stress; its levels reach a plateau after about 2 hr of stress. In contrast to wild type plants, an abscisic acid-deficient mutant of tomato, flc, shows a drastically reduced induction of this gene in response to water stress. High levels of pLE25 transcripts accumulate in mutant and wild type plants upon exogenous application of abscisic acid. Thus, this hormone stimulates the accumulation of the pLE25 transcript.; During the period after the onset of water stress, mRNAs that encode the ribulose-1,5-bisphosphate carboxylase (Rubisco) small subunit decrease, whereas transcript levels of the chloroplast gene psbA remain unchanged. Two hours after re-watering stressed intact plants, the pLE25 transcript is no longer detected.