Map-Based Cloning and Functional Analysis of YE1 in Rice, Which Is Involved in Light-Dependent Chlorophyll Biogenesis and Photoperiodic Flowering Pathway

Abstract

Light is one of the most important environmental factors that affect many aspects of plant growth, including chlorophyll (Chl) synthesis and flowering time. Here, we identified a rice mutant, <i>yellow leaf and early flowering</i> (<i>ye1</i>), and characterized the gene <i>YE1</i> by using a map-based cloning method. <i>YE1</i> encodes a heme oxygenase, which is localized to the chloroplasts. <i>YE1</i> is expressed in various green tissues, especially in leaves, with a diurnal-rhythmic expression pattern, and its transcripts is also induced by light during leaf-greening. The mutant displays decreased Chl contents with less and disorderly thylakoid lamellar layers in chloroplasts, which reduced the photosynthesis rate. The early flowering phenotype of <i>ye1</i> was not photoperiod-sensitive. Furthermore, the expression levels of Chl biosynthetic genes were downregulated in <i>ye1</i> seedlings during de-etiolation responses to light. We also found that rhythmic expression patterns of genes involved in photoperiodic flowering were altered in the mutant. Based on these results, we infer that <i>YE1</i> plays an important role in light-dependent Chl biogenesis as well as photoperiodic flowering pathway in rice.