Drought affects rice reproduction and results in severe yield loss. The developmental defects and changes
of gene regulation network in reproductive tissues under drought stress are largely unknown. In this study, rice plants
subjected to reproductive stage drought stress were examined for floral development and transcriptomic changes.
The results showed that male fertility was dramatically affected, with differing pollen viability in flowers of the same
panicle due to aberrant anther development under water stress. Examination of local starch distribution revealed that
starch accumulated abnormally in terms of position and abundance in anthers of water-stressed plants. Microarray
analysis using florets of different sizes identified >1000 drought-responsive genes, most of which were specifically
regulated in only one or two particular sizes of florets, suggesting developmental stage-dependent responses to
drought. Genes known to be involved in tapetum and/or microspore development, cell wall formation or expansion,
and starch synthesis were found more frequently among the genes affected by drought than genome average, while
meiosis and MADS-box genes were less frequently affected. In addition, pathways related to gibberellin acid signaling
and abscisic acid catabolism were reprogrammed by drought. Our results strongly suggest interactions between
reproductive development, phytohormone signaling, and carbohydrate metabolism in water-stressed plants.