Ascorbate Peroxidase OsAPx1 is Involved in Seed Development in Rice

Abstract

Ascorbate peroxidases (APXs) are enzymes that detoxify peroxides such as hydrogen peroxide using ascorbate. They are distributed as isoenzymes in distinct cellular compartments, such as the cytosol, mitochondria and peroxisomes, where they play essential roles in scavenging reactive oxygen species (ROS) and protecting cells against the toxic effects of these species in higher plants, algae, euglena and other organisms. APXs also respond to environmental stresses, such as salinity and drought, and rice ascorbate peroxidase 1 (OsAPx1) participates in salinity tolerance. However, it is still unclear how OsAPx1 is involved in growth and development before and after flowering. Here, we show that OsAPx1 plays an important function in seed development, including fertilization. Proteomic analysis and quantitative RT-PCR showed that protein and mRNA levels of OsAPx1 were much higher in immature seeds than in mature seeds. Plant height and grain size in an Osapx1 mutant were almost the same as those in wild-type plants. However, about 58% of the seeds were aborted in the Osapx1 mutant, although the mutant was capable of normal flowering. Our results suggest that rice ascorbate peroxidase functions both as a regulator of seed development and as a scavenger of ROS.