THERMOSENSITIVE BARREN PANICLE (TAP) is required for rice panicle and spikelet development at high ambient temperature.

ABSTRACT

In cereal plants, the size of the panicle (inflorescence) is a critical factor for yield. Panicle size is determined by a complex interplay of genetic and environmental factors, but the mechanisms underlying adaptations to temperature stress during panicle development remain largely unknown. We identify the rice THERMOSENSITIVE BARREN PANICLE (TAP) gene, which encodes a transposase-derived FAR1-RELATED SEQUENCE (FRS) protein and is responsible for regulating panicle and spikelet development at high ambient temperature. The tap mutants display high temperature-dependent reproductive abnormalities, including compromised secondary branch and spikelet initiation and pleiotropic floral organ defects. Consistent with its thermosensitive phenotype, TAP expression is induced by high temperature. TAP directly promotes the expression of OsYABBY3 (OsYAB3), OsYAB4, and OsYAB5, which encode key transcriptional regulators in panicle and spikelet development. In addition, TAP physically interacts with OsYAB4 and OsYAB5 proteins; phenotypic analysis of osyab4 tap-1 and osyab5 tap-1 double mutants indicates that TAP-OsYAB4/OsYAB5 complexes act to maintain normal panicle and spikelet development. Taken together, our study reveals the novel role of a TE-derived transcription factor in controlling rice panicle development under high ambient temperatures, shedding light on the molecular mechanism underlying the adaptation of cereal crops to increasing environmental temperatures.