Plant responses to
dehydration stress are mediated by highly complex molecular systems involving
hormone signaling and metabolism, particularly the major stress
hormone abscisic acid (ABA) and ABA-dependent gene expression. To understand the roles of
plant hormones and their interactions during
dehydration, we analyzed the
plant hormone profiles with respect to
dehydration responses in Arabidopsis thaliana wild-type (WT) plants and ABA biosynthesis mutants (nced3-2). We developed a procedure for moderate
dehydration stress, and then investigated temporal changes in the profiles of ABA,
jasmonic acid isoleucine (
JA-Ile),
salicylic acid (SA),
cytokinin (trans-
zeatin, tZ),
auxin (
indole-acetic acid, IAA), and
gibberellin (GA4 ), along with temporal changes in the expression of key genes involved in
hormone biosynthesis. ABA levels increased in a bi-phasic pattern (at the early and late phases) in response to moderate
dehydration stress.
JA-Ile levels increased slightly in WT plants and strongly increased in nced3-2 mutant plants at 72 h after the onset of
dehydration. The expression profiles of
dehydration-inducible genes displayed temporal responses in an ABA-dependent manner. The early phase of ABA accumulation correlated with the expression of touch-inducible genes and was independent of factors involved in the major ABA regulatory pathway, including the ABA-responsive
element-binding (AREB/ABF)
transcription factor.
JA-Ile, SA, and tZ were negatively regulated during the late
dehydration response phase. Transcriptome analysis revealed important roles for
hormone-related genes in metabolism and signaling during
dehydration-induced plant responses.