AUTHOR=Zhang Xiaobo , Wang Ying , Zhu Xiaoyan , Wang Xiaowen , Zhu Zhu , Li Yangyang , Xie Jia , Xiong Yuzhen , Yang Zhenglin , He Guanghua , Sang Xianchun 

TITLE=Curled Flag Leaf 2, Encoding a Cytochrome P450 Protein, Regulated by the Transcription Factor Roc5, Influences Flag Leaf Development in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.616977

DOI=10.3389/fpls.2020.616977

ISSN=1664-462X

ABSTRACT=<p>Moderate curling generally causes upright leaf blades, which favors the establishment of ideal plant architecture and increases the photosynthetic efficiency of the population, both of which are desirable traits for super hybrid rice (<italic>Oryza sativa</italic> L.). In this study, we identified a novel curled-leaf mutant, <italic>curled flag leaf 2</italic> (<italic>cfl2</italic>), which shows specific curling at the base of the flag leaf owing to abnormal epidermal development, caused by enlarged bulliform cells and increased number of papillae with the disordered distribution. Map-based cloning reveals that <italic>CFL2</italic> encodes a cytochrome P450 protein and corresponds to the previously reported OsCYP96B4. <italic>CFL2</italic> was expressed in all analyzed tissues with differential abundance and was downregulated in the <italic>clf1</italic> mutant [a mutant harbors a mutation in the homeodomain leucine zipper IV (HD-ZIP IV) transcription factor <italic>Roc5</italic>]. Yeast one-hybrid and transient expression assays confirm that <italic>Roc5</italic> could directly bind to the <italic>cis</italic>-element L1 box in the promoter of <italic>CFL2</italic> before activating <italic>CFL2</italic> expression. RNA sequencing reveals that genes associated with cellulose biosynthesis and cell wall-related processes were significantly upregulated in the <italic>cfl2</italic> mutant. The components of cell wall, such as lignin, cellulose, and some kinds of monosaccharide, were altered dramatically in the <italic>cfl2</italic> mutant when compared with wild-type “Jinhui10” (WT). Taken together, <italic>CFL2</italic>, as a target gene of <italic>Roc5</italic>, plays an important role in the regulation of flag leaf shape by influencing epidermis and cell wall development.</p>