Overexpression of a CPYC-Type Glutaredoxin, , Causes Abnormal Embryos and an Increased Grain Weight in Rice.

Glutaredoxins (Grxs) are a ubiquitous group of oxidoreductase enzymes that are important in plant growth and development; however, the functions of rice Grxs have not been fully elucidated. In this paper, we showed that one of the Grxs, encoded by , exhibited Grx activity. Furthermore, we demonstrated that was able to regulate embryo development during embryogenesis. Transgenic rice lines overexpressing unexpectedly exhibited degenerate embryos as well as embryoless seeds. Our data indicated that the embryonic abnormalities occurred at an early stage during embryogenesis. We found that the expression of several endodermal layer marker genes for embryo development, such as (apical region marker), (L2 ground tissue marker), and (L3 vascular tissue marker), were significantly decreased in the overexpressed transgenic rice lines. In contrast, the transcript levels of the majority of protodermal layer markers, including , , , and , and the shoot apical meristem marker , showed little change between the wild-type (WT) and -overexpressing embryos. Surprisingly, the seed weight of the overexpressed transgenic rice was remarkably increased in comparison to that of the WT. These results indicate that the overexpression of interferes with the normal embryogenesis of rice embryos and leads to increased grain weight. To the best of our knowledge, this is the first report that is a rice embryo development-associated gene.