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

Abstract

Leaf rolling is considered as one of the most important agronomic traits in rice breeding. It has been previously reported that SEMI-ROLLED LEAF 1 (SRL1) modulates leaf rolling by regulating the formation of bulliform cells in rice (Oryza sativa); 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 loses function in cld1 through DNA methylation. CLD1/SRL1 encodes a glycophosphatidylinositol (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 the loss of function of CLD1/SRL1 affects cell wall formation. Furthermore, the 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. As a result of the more rapid water loss and lower water content in leaves, cld1 exhibits reduced drought tolerance. Accordingly, the 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.

Characterization of the Gh4CL gene family reveals a role of Gh4CL7 in drought tolerance

“…It provides mechanical support to plants by increasing cell wall hardness and enhancing compressive strength of cells [60][61][62]. We found that repressing the expression level of Gh4CL7 in G. hirsutum reduced the lignin content and led to a reduction in drought resistance, consistent with the result of rice plants with a decreased lignin content being more prone to drought stress [63]. Studies in Fraxinus mandshurica also showed that decreased lignin content resulted in drought resistance reduction [24].…”

Overexpression of OsTF1L, a rice HD‐Zip transcription factor, promotes lignin biosynthesis and stomatal closure that improves drought tolerance

“…Drought‐tolerant maize inbred lines under drought stress conditions display higher lignification than drought‐sensitive inbred lines (Hu et al ., ). Also, the curled leaf and dwarf 1 ( cd1 ) mutant exhibit significant decrease in lignin contents in secondary cell walls causing water deficits in cd1 leaves and resulting to reduced drought tolerance (Li et al ., ). In addition, reduced lignification in plants increases their xylem vulnerability to embolism (Voelker et al ., ).…”

“…Regulation of stomatal movement in this regard has been an active research area for drought tolerance. For example, overexpression of OsASR5 , ONAC022 , AtMYB61 , BplMYB46 and PtoMYB170 significantly enhanced drought tolerance in plants by regulation of stomatal closure under drought stress conditions (Guo et al ., ; Hong et al ., ; Li et al ., ; Romano et al ., ; Xu et al ., ). Interestingly, overexpression of AtMYB61 , BplMYB46 and PtoMYB170 also increased lignin biosynthesis.…”

The Temperature-Dependent Retention of Introns in GPI8 Transcripts Contributes to a Drooping and Fragile Shoot Phenotype in Rice

“…T-DNA insertion in OsBC1L4 results in abnormal cell expansion, dwarfing, and fewer tillers in rice [25]. The CLD1/SRL1 gene encodes a GPI-anchored membrane protein that modulates leaf rolling and other aspects of rice growth and development [26,27].…”