Abstract
Adventitious roots (ARs) are formed de novo during post-embryonic development from non-root tissues, in processes that are highly dependent on environmental inputs. Whole root excision from young seedlings has been previously used as a model to study adventitious root formation in Arabidopsis thaliana hypocotyls. To identify novel regulators of adventitious root formation, we analyzed adventitious rooting in the hypocotyl after whole root excision in 112 T-DNA homozygous leaf mutants, which were selected based on the dynamic expression profiles of their annotated genes during hormone-induced and wound-induced tissue regeneration. Forty-seven T-DNA homozygous lines that displayed low rooting capacity as regards their wild-type background were dubbed as the less adventitious roots (lars) mutants. We identified eight lines with higher rooting capacity than their wild-type background that we named as the more adventitious roots (mars) mutants. A relatively large number of mutants in ribosomal protein-encoding genes displayed a significant reduction in adventitious root number in the hypocotyl after whole root excision. In addition, gene products related to gibberellin (GA) biosynthesis and signaling, auxin homeostasis, and xylem differentiation were confirmed to participate in adventitious root formation. Nearly all the studied mutants tested displayed similar rooting responses from excised whole leaves, which suggest that their affected genes participate in shared regulatory pathways required for de novo organ formation in different organs.
Highlights
Adventitious roots (ARs) are formed de novo from non-root tissues after a stress episode, such as drought, flooding or physical damage (Steffens and Rasmussen, 2016)
Whole root excision from young seedlings was previously used as a model to study AR formation in A. thaliana hypocotyls (Correa et al, 2012; Sukumar et al, 2013)
We characterized AR formation in the Col-0 accession, which has been used as a background reference for the Salk Unimutant and GABI-Kat collections of sequence-indexed T-DNA lines (Li et al, 2007; O’Malley and Ecker, 2010)
Summary
Adventitious roots (ARs) are formed de novo from non-root tissues (i.e., stems or leaves) after a stress episode, such as drought, flooding or physical damage (Steffens and Rasmussen, 2016). A local increase in auxin-induced marker expression was observed shortly after whole root excision in a defined region of the hypocotyl with the highest expression localized to xylem pole pericycle cells. This expression pattern was dependent on ATP BINDING CASSETTE SUBFAMILY B 19 (ABCB19)mediated polar auxin transport from the shoot (Sukumar et al, 2013). ARs originate from non-root tissues, such as the vascular cambium, in a process that requires cell dedifferentiation and presumably different regulatory pathways as the hypocotyl-derived ARs (Bellini et al, 2014; Verstraeten et al, 2014)
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