Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 118, Issue 35, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2101526118
Keywords
barley; CRISPR; Cas9; EGT2; gravitropism; root angle
Categories
Funding
- Deutsche Forschungs-gemeinschaft [HO2249/21-1]
- Helmholtz Association for the Forschungszentrum Julich
- European Union [731013]
- Biotechnology and Biological Sciences Research Council in the United Kingdom [BB/S012826/1]
- project Rooty: A root ideotype toolbox to support improved wheat yields - IWYP Consortium [IWYP122]
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The root growth angle is a crucial factor affecting the yield and stress resilience of crop plants. The egt2 gene is involved in regulating the root growth angle in barley and wheat, highlighting its potential as a target for improving root-based crop strategies in cereals.
The root growth angle defines how roots grow toward the gravity vector and is among the most important determinants of root system architecture. It controls water uptake capacity, nutrient use efficiency, stress resilience, and, as a consequence, yield of crop plants. We demonstrated that the egt2 (enhanced gravitropism 2) mutant of barley exhibits steeper root growth of seminal and lateral roots and an auxin-independent higher responsiveness to gravity compared to wild-type plants. We cloned the EGT2 gene by a combination of bulked-segregant analysis and whole genome sequencing. Subsequent validation experiments by an independent CRISPR/Cas9 mutant allele demonstrated that egt2 encodes a STERILE ALPHA MOTIF domain-containing protein. In situ hybridization experiments illustrated that EGT2 is expressed from the root cap to the elongation zone. We demonstrated the evolutionary conserved role of EGT2 in root growth angle control between barley and wheat by knocking out the EGT2 orthologs in the A and B genomes of tetraploid durum wheat. By combining laser capture microdissection with RNA sequencing, we observed that seven expansin genes were transcriptionally down-regulated in the elongation zone. This is consistent with a role of EGT2 in this region of the root where the effect of gravity sensing is executed by differential cell elongation. Our findings suggest that EGT2 is an evolutionary conserved regulator of root growth angle in barley and wheat that could be a valuable target for root-based crop improvement strategies in cereals.
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