Photo-Sensitive Leaf Rolling 1encodes A Polygalacturonase That Modifies Cell Wall Structure And Drought Tolerance In Rice

The biosynthesis and modification of cell wall composition and structure are controlled by hundreds of enzymes and have a direct consequence on plant growth and development. However, the majority of these enzymes has not been functionally characterised. Rice mutants with leaf-rolling phenotypes were screened in a field. Phenotypic analysis under controlled conditions was performed for the selected mutant and the relevant gene was identified by map-based cloning. Cell wall composition was analysed by glycome profiling assay. We identified aphoto-sensitive leaf rolling 1(psl1) mutant with 'napping' (midday depression of photosynthesis) phenotype and reduced growth. ThePSL1gene encodes a cell wall-localised polygalacturonase (PG), a pectin-degrading enzyme.psl1with a 260-bp deletion in its gene displayed leaf rolling in response to high light intensity and/or low humidity. Biochemical assays revealed PG activity of recombinant PSL1 protein. Significant modifications to cell wall composition in thepsl1mutant compared with the wild-type plants were identified. Such modifications enhanced drought tolerance of the mutant plants by reducing water loss under osmotic stress and drought conditions. Taken together, PSL1 functions as a PG that modifies cell wall biosynthesis, plant development and drought tolerance in rice.