Drought is a common abiotic stress for terrestrial plants and often
affects crop development and yield. Recent studies have suggested that
lignin plays a crucial role in plant drought tolerance; however, the
underlying molecular mechanisms are still largely unknown.

Here, we report that the rice (/Oryza sativa/) gene/CINNAMOYL-CoA
REDUCTASE 10/(/OsCCR10/) is directly activated by
the/OsNAC5/transcription factor, which mediates drought tolerance
through regulating lignin accumulation. CCR is the first committed
enzyme in the monolignol synthesis pathway, and the expression of 26 CCR
genes was observed to be induced in rice roots under drought.
Subcellular localisation assays revealed that OsCCR10 is a catalytically
active enzyme that is localised in the cytoplasm. The/OsCCR10/transcript
levels were found to increase in response to abiotic stresses, such as
drought, high salinity, and abscisic acid (ABA), and transcripts were
detected in roots at all developmental stages./

In vitro/enzyme activity and/in vivo/lignin composition assay suggested
that OsCCR10 is involved in H- and G-lignin biosynthesis. Transgenic
rice plants overexpressing/OsCCR10/showed improved drought tolerance at
the vegetative stages of growth, as well as higher photosynthetic
efficiency, lower water loss rates, and higher lignin content in roots
compared to non-transgenic (NT) controls. In contrast,
CRISPR/Cas9-mediated/OsCCR10/knock-out mutants exhibited reduced lignin
accumulation in roots and less drought tolerance. Notably, transgenic
rice plants with root-preferential overexpression of/OsCCR10/exhibited
higher grain yield than NT controls plants under field drought
conditions, indicating that lignin biosynthesis mediated
by/OsCCR10/contributes to drought tolerance.

Transcriptional activation of rice CINNAMOYL�CoA REDUCTASE 10 by OsNAC5,
contributes to drought tolerance by modulating lignin accumulation in
roots - Bang - - Plant Biotechnology Journal - Wiley Online Library
[onlinelibrary.wiley.com]