期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：35
DOI：10.1073/pnas.2101526118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
To date, the potential of utilizing root traits in plant breeding remains largely untapped. In this study, we cloned and characterized the
ENHANCED GRAVITROPISM2 (
EGT2) gene of barley that encodes a STERILE ALPHA MOTIF domain–containing protein. We demonstrated that
EGT2 is a key gene of root growth angle regulation in response to gravity, which is conserved in barley and wheat and could be a promising target for crop improvement 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.
