YELLOW LEAF AND DWARF 7, Encoding a Novel Ankyrin Domain-Containing Protein, Affects Chloroplast Development in Rice

Background: The proper development of grana and stroma within chloroplasts is critical for plant vitality and crop yield in rice and other cereals. While the molecular mechanisms underpinning these processes are known, the genetic networks governing them require further exploration. Methods and Results: In this study, we characterize a novel rice mutant termed yellow leaf and dwarf 7 (yld7), which presents with yellow, lesion-like leaves and a dwarf growth habit. The yld7 mutant shows reduced photosynthetic activity, lower chlorophyll content, and abnormal chloroplast structure. Transmission electron microscopy (TEM) analysis revealed defective grana stacking in yld7 chloroplasts. Additionally, yld7 plants accumulate high levels of hydrogen peroxide (H₂O₂) and exhibit an up-regulation of senescence-associated genes, leading to accelerated cell death. Map-based cloning identified a C-to-T mutation in the LOC_Os07g33660 gene, encoding the YLD7 protein, which is a novel ankyrin domain-containing protein localized to the chloroplast. Immunoblot analysis of four LHCI proteins indicated that the YLD7 protein plays an important role in the normal biogenesis of chloroplast stroma and grana, directly affecting leaf senescence and overall plant stature. Conclusions: This study emphasizes the significance of YLD7 in the intricate molecular mechanisms that regulate the structural integrity of chloroplasts and the senescence of leaves, thus providing valuable implications for the enhancement of rice breeding strategies and cultivation.