Figure 4. Light signaling pathways contributing to drought
tolerance.
Drought stress results in biosynthesis of ABA leading to ABA-dependent
gene regulation causing drought tolerance. In addition, stomata close
preventing water loss via transpiration. Under shade conditions (low
R:FR ratio), ABA biosynthesis is stimulated which results in the
induction of ABA-induced gene expression causing drought tolerance. Low
R:FR ratios also increase the sensitivity to ABA causing increased
drought tolerance. Also, phyB acts on stomatal opening in a COP1- or
PIF3/PIF4-dependent way to regulate stomatal closure. Blue light
perceived by CRY1 and PHOT1/PHOT2 represses the inhibitory function of
COP1 on stomatal opening resulting in closed stomata thereby increasing
drought tolerance. For more information concerning the different
pathways, please refer to section 4. Abbreviations: ABA, abscisic acid;
R, red light; FR, far-red light; B, blue light.