Drought is the major environmental factor limiting crop productivity worldwide. We hypothesized
that it is possible to enhance drought tolerance by delaying stress-induced senescence
through the stress-induced synthesis of cytokinins in crop-plants. We generated transgenic
rice (Oryza sativa) plants expressing an isopentenyltransferase (IPT) gene driven by PSARK, a
stress- and maturation-induced promoter. Plants were tested for drought tolerance at two
yield-sensitive developmental stages: pre- and post-anthesis. Under both treatments, the
transgenic rice plants exhibited delayed response to stress with significantly higher grain yield
(GY) when compared to wild-type plants. Gene expression analysis revealed a significant shift
in expression of hormone-associated genes in the transgenic plants. During water-stress (WS),
PSARK::IPT plants displayed increased expression of brassinosteroid-related genes and repression
of jasmonate-related genes. Changes in hormone homeostasis were associated with
resource(s) mobilization during stress. The transgenic plants displayed differential expression
of genes encoding enzymes associated with hormone synthesis and hormone-regulated
pathways. These changes and associated hormonal crosstalk resulted in the modification of
source ⁄sink relationships and a stronger sink capacity of the PSARK::IPT plants during WS. As a
result, the transgenic plants had higher GY with improved quality (nutrients and starch