CLD1/SRL1 modulates leaf rolling by affecting cell wall formation, epidermis integrity and water homeostasis in rice

Summary Leaf rolling is considered as one of the most important agronomic traits in rice breeding. It has been previously reported that SEMI-ROLLED LEAF1 (SRL1) modulates leaf rolling by regulating the formation of bulliform cells in rice. However, the regulatory mechanism underlying SRL1 has yet to be further elucidated. Here, we report the functional characterization of a novel leaf rolling mutant, curled leaf and dwarf 1 (cld1), with multiple morphological defects. Map-based cloning revealed that CLD1 is allelic with SRL1 and loss its function in cld1 through DNA methylation. CLD1/SRL1 encodes a GPI-anchored membrane protein that modulates leaf rolling and other aspects of rice growth and development. The cld1 mutant exhibits significant decreases in cellulose and lignin contents in secondary cell walls of leaves, indicating that loss-of-function of CLD1/SRL1 affects cell wall formation. Furthermore, loss of CLD1/SRL1 function leads to defective leaf epidermis such as bulliform-like epidermal cells. The defects in leaf epidermis decrease the water-retaining capacity and lead to water deficits in cld1 leaves, which contribute to the main cause of leaf rolling. Due to the more rapid water loss and lower water content in leaves, cld1 exhibits reduced drought tolerance. Accordingly, loss of CLD1/SRL1 function causes abnormal expression of genes and proteins associated with cell wall formation, cuticle development and water stress. Taken together, these findings suggest that the functional roles of CLD1/SRL1 in leaf rolling regulation are closely related to the maintenance of cell wall formation, epidermal integrity and water homeostasis. This article is protected by copyright. All rights reserved.