Not all wall-loosening proteins can help root hairs grow
Zhou K, Hepler NK, Jia M, Cosgrove DJ
Crispr
The fine root hairs that let your tomatoes, native wildflowers and street trees drink and feed from the soil depend on wall-loosening proteins, and this work shows which versions actually do the job, a step toward breeding plants with better roots for drought and poor soil.
Root hairs are tiny tubes that stretch out from roots to soak up water and nutrients. To grow, their walls must loosen, and a family of proteins called expansins does that work. Scientists removed two of these proteins in a small mustard-family plant and root hairs stopped growing, then tested which other expansins could step in. Some fully replaced them, some only helped a little, and some did nothing, often because they were missing one key building block.
Key Findings
CRISPR knockout of the two root hair expansin genes EXPA7 and EXPA18 in Arabidopsis abolished root hair elongation.
Expansins from different clades gave full, partial, or no rescue; EXPA13 (clade VIII) and EXPA20 (clade IX) failed, and both lack a conserved Asp residue. Loss of this Asp may predate angiosperms.
Mutating the Asp in EXPA7 destroyed its activity, but restoring it in EXPA13 did not rescue function, and EXPB, EXLA and EXLB family members all failed to restore root hair growth.
chevron_right Technical Summary
Root hairs, the tiny threads that soak up water and nutrients, need specific wall-loosening proteins called expansins to grow. Researchers found that different expansin types are not interchangeable: some fully rescue root hair growth in mutant plants, while others fail, often because they lack a single key amino acid.
Abstract Preview
Original paper
Functional divergence of plant expansins as revealed by genetic complementation of root-hair tip growth in Arabidopsis thaliana.
Plant cell wall expansion is essential for plant growth, with expansins promoting wall creep during diffuse growth. Expansin's role in tip growth, such as root hair elongation, is less clear. Here,...
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