Calcium: A Pivotal Regulator of Panicle Apical Abortion in Rice

Panicle size is a critical determinant of grain yield in rice and other cereal crops. During rice growth and development, panicle apical abortion (PAA) frequently occurs, particularly under unfavorable conditions, resulting in a reduced number of fertile spikelets and substantial yield losses. In production practice, PAA is a quantitative trait regulated by both genetic and environmental factors. To date, no major quantitative trait loci (QTLs) underlying PAA have been successfully cloned from elite rice cultivars. Studies of PAA-related mutants suggest that this trait involves multiple biological processes. In this review, we synthesize current evidence and propose a pivotal role of calcium in young panicle development. We conclude that PAA is closely associated with disrupted Ca 2+ homeostasis and aberrant calcium signaling.