Effects of a Coumarin Derivative, 4-Methylumbelliferone,on Seed Germination and Seedling Establishment in <Emphasis Type="Italic">Arabidopsis</Emphasis> |
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Authors: | Xiang?Li Margaret?Y?Gruber Dwayne?D?Hegedus Derek?J?Lydiate Email author" target="_blank">Ming-Jun?GaoEmail author |
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Affiliation: | (1) College of Plant Sciences, Jilin University, Changchun, 130062, China;(2) Agriculture and Agri-Food Canada, Saskatoon Research Centre, Saskatoon, Saskatchewan, S7N 0X2, Canada; |
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Abstract: | The root system is central for plant adaptation to soil heterogeneity and is organized primarily by root branching. To search
for compounds that regulate root branching, a forward chemical genetics screen was employed, and 4-methylumbelliferone (4-MU),
a coumarin derivative, was found to be a potent regulator of lateral root formation. Exogenous application of 4-MU to Arabidopsis thaliana seeds affected germination and led to reduced primary root growth, the formation of bulbous root hairs, and irregular detached
root caps accompanied by reorganization of the actin cytoskeleton in root tips before seedling establishment. Abundant lateral
roots formed after exposure to 125 μM 4-MU for 22 days. Molecular, biochemical, and phytochemical approaches were used to
determine the effect of 4-MU on root growth and root branching. Arabidopsis seedlings grown in the presence of 4-MU accumulated this compound only in roots, where it was partially transformed by UDP-glycosyltransferases
(UGTs) into 4-methylumbelliferyl-β-D-glucoside (4-MU-Glc). The presence of 4-MU-Glc in seedling roots was consistent with the upregulation of several genes
that encode UGTs in the roots. This shows that UGTs play an integral role in the detoxification of 4-MU in plants. The increased
expression of two auxin efflux facilitator genes (PIN2 and PIN3) in response to 4-MU and the lack of response of the auxin receptor TIR1 and the key auxin biosynthetic gene YUCCA1 suggest that auxin redistribution, rather than auxin biosynthesis, may directly or indirectly mediate 4-MU-induced root branching. |
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