It has been reported that ATP synthesis during drought stress is essential for preserving plastid function [ 74].
It has been reported that in barley and bean, drought stress could result in high levels of ABA by 57 160 times, compared with those of controls.
However, pollen dehydration does not seem to affect Atppc4 expression, because Atppc4 expression started after PMII, but was not sustained until anthesis, although it has been reported that Atppc4 expression is inducible by drought stress in root tissues [ 29].
Interestingly, it has been reported that SnRK2 and HPT1 were involved in drought stress response through ABA signaling pathway and tocopherol biosynthesis, respectively [ 75, 76].
It has been reported that miR169g is the only member induced by drought in the miR169 family of rice and its expression is regulated by drought [ 17].
It has been reported that more genes are upregulated than are downregulated under drought stress in model plants [ 32].
Yu et al. (2014) calculated the standardized precipitation evapotranspiration index (SPEI) and reported that drought was becoming more severe since the late 1990s in most parts of China and that the drying area increased by 3.72 % per decade.
Previously, it was reported that OsHsfC1b expression is induced by drought stress (Hu et al. 2009), which causes osmotic imbalance as well.
It was reported that OsCPK15 was induced in response to drought stress in roots of rice, and salt stress [ 54].
Recently, it was reported that in Nipponbare rice, enhanced expression of sucrose transporters (OsSUT2) in source leaves under drought was associated with greater drought tolerance (Ibraheem et al. 2011).
