A hierarchical abscission program regulates reproductive allocation in Prunus yedoensis and Prunus sargentii

Abstract

O_LIorgan abscission is essential for optimal reproduction, yet its regulation in perennial woody plant species is poorly understood. To investigate how abscission is spatially and temporally regulated during reproduction, we analyzed five sequential abscission events in the cherry species Prunus yedoensis and Prunus sargentii: abscission of the petals, calyces, flower pedicels, fruit pedicels, and peduncles. C_LIO_LIThe abscission zone (AZ) of the calyx formed de novo upon activation, whereas other AZs were pre-formed but developmentally arrested. Localized ethylene responsiveness reactivated these zones, promoting cell division, differentiation of residuum and secession cells on either side of the AZ, and lignin deposition in some cases. This progression was accompanied by reactive oxygen species accumulation and pH shifts. C_LIO_LIWe observed species-specific differences during early floral abscission: P. yedoensis shed petals rapidly in a pollination-independent manner, whereas P. sargentii retained petals on unpollinated flowers, which later abscised with the pedicel, potentially extending the fertilization window. C_LIO_LIBoth species employed a post-fertilization checkpoint via fruit pedicel abscission to selectively eliminate small, slow-growing fruits. These findings reveal that Prunus species coordinate a hierarchical abscission program functioning as a multilayered reproductive filter, progressively refining investment decisions to determine the final fruit set. C_LI