Global transcriptome and gene co-expression network analyses reveal
regulatory and non-additive effects of drought and heat stress in
grapevine
Abstract
Despite frequent co-occurrence of drought and heat stress, the molecular
mechanisms governing plant responses to these stresses in combination
have not often been studied. This is particularly evident in non-model,
perennial plants. We conducted large scale physiological and
transcriptome analyses to identify genes and pathways associated with
grapevine response to drought and/or heat stress during stress
progression and recovery. We identified gene clusters with expression
correlated to leaf temperature and water stress and five hub genes for
the combined stress co-expression network. Several differentially
expressed genes were common to the individual and combined stresses, but
the majority were unique to the individual or combined stress
treatments. These included heat-shock proteins, mitogen-activated
kinases, sugar metabolizing enzymes, and transcription factors, while
phenylpropanoid biosynthesis and histone modifying genes were unique to
the combined stress treatment. Following physiological recovery,
differentially expressed genes were found only in plants under heat
stress, both alone and combined with drought. Taken collectively, our
results suggest that the effect of the combined stress on physiology and
gene expression is more severe than that of individual stresses, but not
simply additive, and that epigenetic chromatin modifications may play an
important role in grapevine responses to combined drought and heat
stress.