Cell/Development/Systems

Abstract

CS -15-6 - CRISPR/Cas9-mediated genome editing reveals Arabidopsis thaliana expansin paralogs AtEXPA7 and AtEXPA18 function redundantly and are required for proper root hair formation.

Monday, July 16
2:43 PM - 2:45 PM

Root hair formation can be divided into two distinct stages: initiation and elongation. During both of these stages, structural rearrangements occur within the cell walls of root hair-bearing epidermal cells. Wall modifying proteins are key players in this process, but the extent of their roles remains unclear. One such class of proteins believed to be critical in root hair development is expansins, the mediators of acid growth. Expression analyses in Arabidopsis thaliana (Col-0) indicate expansins AtEXPA7 and AtEXPA18, the two paralogs of clade EXPA-X, specifically localize to root hair progenitor cells and elongated root hairs. For exploring the roles of these two expansins in root hair development, we utilized CRISPR/Cas9-mediated genome editing and a polycistronic tRNA-gRNA system for simultaneously targeting both expansin loci using a single vector. Interestingly, atexpa7 and atexpa18 single knock out mutants were found to produce elongated root hairs, indicating that a single paralog is sufficient for root hair elongation.  However, atexpa7/atexpa18 mutants failed to display elongated root hairs and instead exhibit only small bulges, indicative of root hair initiation but a cessation of further development. The atexpa7/atexpa18 genotype segregated with the “hairless” phenotype, confirming lack of root hair elongation is a result of EXPA-X loss. Furthermore, overall root lengths for atexpa7/atexpa18 plants were significantly reduced, which was found to be attributable to a reduced root growth rate. Complementation using either AtEXPA7 or AtEXPA18 was sufficient to restore proper root hair development in atexpa7/atexpa18 plants, further illustrating EXPA-X’s importance in elongation. Surprisingly, no change in root hair density was observed for either single or double knock out plants.Taken together, these results reveal that while AtEXPA7 and AtEXPA18 together are critical for root hair elongation, they act independently from root hair initiation, suggesting additional expansins may be separately involved during the first stage of root hair growth.


 

Co-Authors

Moyan Jia – The Pennsylvania State University; Daniel Cosgrove – The Pennsylvania State University

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Assets

CS -15-6 - CRISPR/Cas9-mediated genome editing reveals Arabidopsis thaliana expansin paralogs AtEXPA7 and AtEXPA18 function redundantly and are required for proper root hair formation.



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Send Email for CRISPR/Cas9-mediated genome editing reveals Arabidopsis thaliana expansin paralogs AtEXPA7 and AtEXPA18 function redundantly and are required for proper root hair formation.