Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation
Plant myrosinases (β-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remain...
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MDPI AG
2016-06-01
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Online Access: | http://www.mdpi.com/1422-0067/17/6/892 |
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DOAJ |
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English |
format |
Article |
sources |
DOAJ |
author |
Lili Fu Meng Wang Bingying Han Deguan Tan Xuepiao Sun Jiaming Zhang |
spellingShingle |
Lili Fu Meng Wang Bingying Han Deguan Tan Xuepiao Sun Jiaming Zhang Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation International Journal of Molecular Sciences myrosinase root-tip AtTGG4 AtTGG5 DR5 flood tolerance double mutant |
author_facet |
Lili Fu Meng Wang Bingying Han Deguan Tan Xuepiao Sun Jiaming Zhang |
author_sort |
Lili Fu |
title |
Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation |
title_short |
Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation |
title_full |
Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation |
title_fullStr |
Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation |
title_full_unstemmed |
Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation |
title_sort |
arabidopsis myrosinase genes attgg4 and attgg5 are root-tip specific and contribute to auxin biosynthesis and root-growth regulation |
publisher |
MDPI AG |
series |
International Journal of Molecular Sciences |
issn |
1422-0067 |
publishDate |
2016-06-01 |
description |
Plant myrosinases (β-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both genes were expressed in the root-tip but with difference: AtTGG4 was expressed in the elongation zone of the root-tip, while AtTGG5 was expressed in the whole root-tip. Moreover, myrosin cells that produce and store the Myr I myrosinases in aboveground organs were not observed in roots, and AtTGG4 and AtTGG5 were expressed in all cells of the specific region. A homozygous double mutant line tgg4tgg5 was obtained through cross-pollination between two T-DNA insertion lines, tgg4E8 and tgg5E12, by PCR-screening in the F2 and F3 generations. Analysis of myrosinase activity in roots of mutants revealed that AtTGG4 and AtTGG5 had additive effects and contributed 35% and 65% myrosinase activity in roots of the wild type Col-0, respectively, and myrosinase activity in tgg4tgg5 was severely repressed. When grown in Murashiege & Skoog (MS) medium or in soil with sufficient water, Col-0 had the shortest roots, and tgg4tgg5 had the longest roots, while tgg4E8 and tgg5E12 had intermediate root lengths. In contrast, when grown in soil with excessive water, Col-0 had the longest roots, and tgg4tgg5 had the shortest roots. These results suggested that AtTGG4 and AtTGG5 regulated root growth and had a role in flood tolerance. The auxin-indicator gene DR5::GUS was then introduced into tgg4tgg5 by cross-pollination. DR5::GUS expression patterns in seedlings of F1, F2, and F3 generations indicated that AtTGG4 and AtTGG5 contributed to auxin biosynthesis in roots. The proposed mechanism is that indolic glucosinolate is transported to the root-tip and converted to indole-3-acetonitrile (IAN) in the tryptophan-dependent pathways by AtTGG4 and AtTGG5, and IAN is finally converted to indole-3-acetic acid (IAA) by nitrilases in the root-tip. This mechanism guarantees the biosynthesis of IAA in correct cells of the root-tip and, thus, a correct auxin gradient is formed for healthy development of roots. |
topic |
myrosinase root-tip AtTGG4 AtTGG5 DR5 flood tolerance double mutant |
url |
http://www.mdpi.com/1422-0067/17/6/892 |
work_keys_str_mv |
AT lilifu arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation AT mengwang arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation AT bingyinghan arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation AT deguantan arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation AT xuepiaosun arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation AT jiamingzhang arabidopsismyrosinasegenesattgg4andattgg5areroottipspecificandcontributetoauxinbiosynthesisandrootgrowthregulation |
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doaj-b3b483085f2c413f8efc4e23d8b610632020-11-24T20:44:36ZengMDPI AGInternational Journal of Molecular Sciences1422-00672016-06-0117689210.3390/ijms17060892ijms17060892Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth RegulationLili Fu0Meng Wang1Bingying Han2Deguan Tan3Xuepiao Sun4Jiaming Zhang5Institute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaInstitute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaInstitute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaInstitute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaInstitute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaInstitute of Tropical Bioscience and Biotechnology, Key Laboratory of Tropical Crops Biology and Genetic Resources, Ministry of Agriculture; Hainan Bioenergy Center, Chinese Academy of Tropical Agricultural Sciences, Xueyuan Road 4, Haikou 571101, ChinaPlant myrosinases (β-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both genes were expressed in the root-tip but with difference: AtTGG4 was expressed in the elongation zone of the root-tip, while AtTGG5 was expressed in the whole root-tip. Moreover, myrosin cells that produce and store the Myr I myrosinases in aboveground organs were not observed in roots, and AtTGG4 and AtTGG5 were expressed in all cells of the specific region. A homozygous double mutant line tgg4tgg5 was obtained through cross-pollination between two T-DNA insertion lines, tgg4E8 and tgg5E12, by PCR-screening in the F2 and F3 generations. Analysis of myrosinase activity in roots of mutants revealed that AtTGG4 and AtTGG5 had additive effects and contributed 35% and 65% myrosinase activity in roots of the wild type Col-0, respectively, and myrosinase activity in tgg4tgg5 was severely repressed. When grown in Murashiege & Skoog (MS) medium or in soil with sufficient water, Col-0 had the shortest roots, and tgg4tgg5 had the longest roots, while tgg4E8 and tgg5E12 had intermediate root lengths. In contrast, when grown in soil with excessive water, Col-0 had the longest roots, and tgg4tgg5 had the shortest roots. These results suggested that AtTGG4 and AtTGG5 regulated root growth and had a role in flood tolerance. The auxin-indicator gene DR5::GUS was then introduced into tgg4tgg5 by cross-pollination. DR5::GUS expression patterns in seedlings of F1, F2, and F3 generations indicated that AtTGG4 and AtTGG5 contributed to auxin biosynthesis in roots. The proposed mechanism is that indolic glucosinolate is transported to the root-tip and converted to indole-3-acetonitrile (IAN) in the tryptophan-dependent pathways by AtTGG4 and AtTGG5, and IAN is finally converted to indole-3-acetic acid (IAA) by nitrilases in the root-tip. This mechanism guarantees the biosynthesis of IAA in correct cells of the root-tip and, thus, a correct auxin gradient is formed for healthy development of roots.http://www.mdpi.com/1422-0067/17/6/892myrosinaseroot-tipAtTGG4AtTGG5DR5flood tolerancedouble mutant |