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Title: Genetic Interactions Between BEN1 ‐ and Cytochrome P450‐Mediated Brassinosteroid Inactivation

Brassinosteroids (BRs) are essential plant growth‐promoting hormones involved in many processes throughout plant development, from seed germination to flowering time. SinceBRsdo not undergo long‐distance transport, cell‐ and tissue‐specific regulation of hormone levels involves both biosynthesis and inactivation. To date, tenBR‐inactivating enzymes, with at least five distinct biochemical activities, have been experimentally identified in the model plantArabidopsis thaliana. Epigenetic interactions betweenT‐DNAinsertion alleles and genetic linkage have hindered analysis of higher‐order null mutants in these genes. A previous study demonstrated that thebas1‐2 sob7‐1 ben1‐1triple‐null mutant could not be characterized due to epigenetic interactions between the exonicT‐DNAinsertions inbas1‐2andsob7‐1,causing the intronicT‐DNAinsertion ofben1‐1to revert to a partial loss‐of‐function allele. We usedCRISPR‐Cas9genome editing to avoid this problem and generated thebas1‐2 sob7‐1 ben1‐3triple‐null mutant. This triple‐null mutant resulted in an additive seedling long‐hypocotyl phenotype. We also uncovered a role forBEN1‐mediatedBR‐inactivation in seedling cotyledon petiole elongation that was not observed in the singleben1‐2null mutant but only in the absence of bothBAS1andSOB7. In addition, genetic analysis demonstrated thatBEN1does not contribute to the early‐flowering phenotype, whichBAS1andSOB7redundantly regulate. Our results show thatBAS1,BEN1,andSOB7have overlapping and independent roles based on their differential spatiotemporal tissue expression patterns

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Physiologia Plantarum
Medium: X
Sponsoring Org:
National Science Foundation
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