A Fragment Substitution in Promoter of MS92/PTC1 Causes Male Sterility in Rice

Abstract

Persistent tapetal cell1 (PTC1) plays a curial role in pollen development, and is thought to function as a transcriptional activator in rice. However, the molecular mechanism of PTC1 in regulating pollen development and its cis-elements are not well understood. We identified a novel weak male sterility mutant (ms92) which exhibited expanded tapetum and shrink pollen grains. Map-based cloning and allelic analysis suggested that the male sterility of ms92 was caused by a DNA fragment substitution in the promoter of PTC1. The decreased expression of MS92/PTC1 in ms92 and cis-element analysis indicated that the substituted sequence contained several potential binding cis-element of negative feedback. MS92/PTC1 was specifically expressed in tapetum and microspores at the young microspore stage, and its protein was localized in nucleus. We further found that MS92/PTC1 functions as a transcription activator by recognizing H3K4me3. Transcriptomic analysis revealed that a number of genes involved in tapetum degeneration and pollen wall formation were down-regulated in ms92, which are the potential targets of MS92/PTC1. The substitution fragment in MS92/PTC1 promoter was essential for pollen development, and we provided a novel mutant for further identifying the cis-elements in promoter and the molecular network of MS92/PTC1.