GH3 phylogenetic subgroups define divergent routes of auxin inactivation via aspartate and glutamine conjugation.
Helusová L, Ušák D, Havránková Z, Dobrev PI, Svobodová B
Plant Signaling
Every time you pinch a stem tip to make a houseplant branch, or watch a cutting sprout roots in water, auxin is the hormone running the show — and now we know plants have two separate molecular off-switches for it, which may explain why some plants are easier to root or train than others.
Plants produce a growth hormone called auxin that controls how they grow, branch, and form roots. To keep growth in check, plants chemically tag auxin with other molecules to deactivate it. This research found that two different families of the enzymes doing that tagging each use a different molecule as the tag, and that this division of labor has been preserved across many plant species over millions of years.
Key Findings
NtGH3.1a (and its Arabidopsis counterpart AtGH3.1) preferentially conjugates auxin (IAA) with aspartate, producing IAA-Asp as the main inactivation product.
NtGH3.6e (and Arabidopsis AtGH3.5/6) preferentially conjugates auxin with glutamine, producing the less-studied conjugates IAA-Gln and oxIAA-Gln.
Both enzyme types localize to the nucleus and cytoplasm regardless of auxin levels, suggesting their distribution is not dynamically regulated by the hormone they inactivate.
chevron_right Technical Summary
Plants use special enzymes to deactivate the growth hormone auxin by attaching different amino acids to it. This study shows that two families of these enzymes have distinct preferences — one favors aspartate, the other glutamine — a division that is conserved across plant species.
Abstract Preview
Auxin conjugation represents a key metabolic mechanism in regulating auxin activity within plant cells. GRETCHEN HAGEN3 (GH3) enzymes conjugate the major naturally occurring auxin indole-3-acetic a...
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