Abnormal meiocytes and tapetum 1 ( <scp>OsAMT1</scp> ) is essential for proper meiosis and tapetal development in rice

In higher plants, both normal meiosis and timely degradation of tapetal cells are crucial for gametophyte development, and abnormal reactive oxygen species (ROS) levels are detrimental to this process. However, the molecular mechanisms underlying their coordination remain unclear. Here, we isolated and characterized a sterile rice mutant, designated as abnormal meiocytes and tapetum 1 (Osamt1). Compared with the wild-type (WT), Osamt1 mutant plants exhibited meiotic chromosomal fragmentation, arrest of pollen mother cell development at meiotic prophase I, abnormal tapetal development, and excessive accumulation of ROS. Map-based cloning revealed that the OsAMT1 gene encodes a protein containing a DUF1771 domain with a Small MutS-related (SMR) domain, whose function is related to DNA repair. Sequence analysis revealed that a single-nucleotide mutation occurred at the splice site between the 5th exon and its adjacent intron of Osamt1, leading to a longer transcript than that in the WT. This aberrant splicing resulted in a frameshift and consequently introduced a premature stop codon. Subcellular localization showed that OsAMT1 is localized to the endoplasmic reticulum (ER). Tissue expression analysis demonstrated that OsAMT1 is strongly expressed in tapetal cells during the early stage of anther development. Biochemical analyses further established that OsAMT1 can physically interact with OsMT2b, a key mediator of ROS scavenging. Further RT-qPCR assays indicated that OsAMT1 affects the reproductive process by influencing the expression of genes related to meiosis and tapetal development. Collectively, our study identifies OsAMT1 as a key regulator of meiosis and tapetum development, expanding the network of reproductive development in rice.