Data from: The role of auxin-mediated gene activation in the bryophyte, Physcomitrium patens

Perception and response to the hormone auxin are critical to plant growth
and development. Expression of auxin-response genes is tightly regulated
via known mechanisms of both activation and repression. Across the plant
lineage, auxin-response gene induction is performed by AUXIN-RESPONSE
FACTOR (ARF), activating transcription factors. Conversely, AUXIN/INDOLE
ACETIC ACID proteins repress expression. Studies of gain-of-function
constitutive-repression lines and ARF loss-of-function mutants have
advanced the field. Yet, there is a need for a comparative study of
aberrant auxin-signaling mutants to understand the developmental
consequences of constitutive repression versus the absence of
auxin-mediated gene induction. Using CRISPR/Cas9 gene-editing tools, we
mutated each activating ARF gene in the model bryophyte, Physcomitrium
patens. The resulting septuple loss-of-function mutant line (arfasept) has
severe developmental phenotypes and a diminished ability to respond to
exogenous auxin. However, phenotypic analysis revealed that the arfasept
line is not as severely affected as the constitutive-repression lines.
Expression analysis of several auxin-response genes demonstrates that
auxin-mediated gene induction is abolished in both arfasept
and constitutive-repression lines but that basal expression
levels are higher in the arfasept lines. Our results suggest that the
expression of auxin-regulated genes important for developmental
progression is maintained, albeit at reduced levels, in the absence of
ARFs.