Root cone angle is enlarged in docs1 LRR-RLK mutants in rice

Background: The DEFECTIVE IN OUTER CELL LAYER SPECIFICATION 1 (DOCS1) gene belongs to the Leucine-Rich Repeat Receptor-Like Kinase (LRR-RLK) subfamily. It has been discovered few years ago in Oryza sativa (rice) in a screen to isolate mutants with defects in sensitivity to aluminum. The c68 (docs1–1) mutant possessed a nonsense mutation in the C-terminal part of the DOCS1 kinase domain. Findings: We have generated a new loss-of-function mutation in the DOCS1 gene (docs1–2) using the CRISPR-Cas9 technology. This new loss-of-function mutant and docs1–1 present similar phenotypes suggesting the original docs1–1 was a null allele. Besides the aluminum sensitivity phenotype, both docs1 mutants shared also several root phenotypes described previously: less root hairs and mixed identities of the outer cell layers. Moreover, our new results suggest that DOCS1 could also play a role in root cap development. We hypothesized these docs1 root phenotypes may affect gravity responses. As expected, in seedlings, the early gravitropic response was delayed. Furthermore, at adult stage, the root gravitropic set angle of docs1 mutants was also affected since docs1 mutant plants displayed larger root cone angles. Conclusions: All these observations add new insights into the DOCS1 gene function in gravitropic responses at several stages of plant development.