InPSR26 Encoding a Putative Membrane Protein Is Involved in Programmed Cell Death during Petal Senescence of Japanese Morning Glory (Ipomoea nil)

The onset and progression of petal senescence, which is a type of programmed cell death (PCD), are tightly controlled by multiple genes. Genes showing changes in expression during petal senescence in Japanese morning glory (Ipomoea nil) were isolated and examined to elucidate their function in PCD. We show here that a putative membrane protein, InPSR26, regulates progression of PCD during petal senescence in I. nil. InPSR26 is most abundantly expressed in petal limbs and its transcript level increases prior to visible senescence symptoms. Transgenic plants with reduced InSPR26 expression (SPR26r lines) showed accelerated petal wilting, with PCD symptoms including cell collapse, ion and anthocyanin leakage and DNA degradation, in petals compared to wild-type plants. Transcript levels of autophagy-related genes (InATG4 and InATG8) were reduced in the petals of PSR26r plants. These results suggest that InPSR26 acts to delay the progression of PCD during petal senescence, possibly through regulation of the autophagic process.