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Arabidopsis thaliana AUCSIA-1 regulates auxin biology and physically interacts with a kinesin-related protein.

Molesini B, Pandolfini T, Pii Y, Korte A, Spena A - PLoS ONE (2012)

Bottom Line: Two allelic mutants for AtAucsia-1 gene did not display visible root morphological alterations; however both basipetal and acropetal indole-3-acetic acid (IAA) root transport was reduced as compared with wild-type plants.The transcript steady state levels of the auxin efflux transporters ATP BINDING CASSETTE subfamily B (ABCB) ABCB1, ABCB4 and ABCB19 were reduced in ataucsia-1 plants.Gene ontology predictions for the two proteins are consistent with the hypothesis that the AtAUCSIA-1/AtAUCSIA-1IP complex is involved in the regulation of the cytoskeleton dynamics underlying auxin biology.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, University of Verona, Verona, Italy.

ABSTRACT
Aucsia is a green plant gene family encoding 44-54 amino acids long miniproteins. The sequenced genomes of most land plants contain two Aucsia genes. RNA interference of both tomato (Solanum lycopersicum) Aucsia genes (SlAucsia-1 and SlAucsia-2) altered auxin sensitivity, auxin transport and distribution; it caused parthenocarpic development of the fruit and other auxin-related morphological changes. Here we present data showing that the Aucsia-1 gene of Arabidopsis thaliana alters, by itself, root auxin biology and that the AtAUCSIA-1 miniprotein physically interacts with a kinesin-related protein. The AtAucsia-1 gene is ubiquitously expressed, although its expression is higher in roots and inflorescences in comparison to stems and leaves. Two allelic mutants for AtAucsia-1 gene did not display visible root morphological alterations; however both basipetal and acropetal indole-3-acetic acid (IAA) root transport was reduced as compared with wild-type plants. The transcript steady state levels of the auxin efflux transporters ATP BINDING CASSETTE subfamily B (ABCB) ABCB1, ABCB4 and ABCB19 were reduced in ataucsia-1 plants. In ataucsia-1 mutant, lateral root growth showed an altered response to i) exogenous auxin, ii) an inhibitor of polar auxin transport and iii) ethylene. Overexpression of AtAucsia-1 inhibited primary root growth. In vitro and in vivo protein-protein interaction experiments showed that AtAUCSIA-1 interacts with a 185 amino acids long fragment belonging to a 2712 amino acids long protein of unknown function (At4g31570). Bioinformatics analysis indicates that the AtAUCSIA-1 interacting protein (AtAUCSIA-1IP) clusters with a group of CENP-E kinesin-related proteins. Gene ontology predictions for the two proteins are consistent with the hypothesis that the AtAUCSIA-1/AtAUCSIA-1IP complex is involved in the regulation of the cytoskeleton dynamics underlying auxin biology.

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Effects of exogenous IAA and ACC on ataucsia-1 root growth.(A) Root phenotype of 10 days old wild-type and ataucsia-1 seedlings after treatment with IAA (0.03 and 0.1 µM). (B) Quantification of IAA effect on root growth. Seeds of wild-type and ataucsia-1 were germinated on nutrient medium for 5 days and then transferred to new medium either supplemented or not supplemented with IAA (0, 0.03 and 0.1 µM). Five days later, new root growth was evaluated. (Left) New primary root growth was measured and plotted as percentage of root growth on medium without IAA. (Right) Weight of root apparatus per cm of primary root length. (C) Quantification of ACC effect on root growth. As performed for panel B, 5 days old seedlings were transferred to medium supplemented or not with ACC (0, and 1 µM). Five days later, root growth was evaluated. (Left) Primary root growth. (Right) Two sets of y-axes are reported, on the left y-axis the weight of root apparatus per cm of primary root length and on the right y-axis the density of emerged lateral roots (number of lateral roots per cm of primary root). The values reported in B and C are means ± SE (n = 3) 15–20 seedlings per replicate. Student's t-test was applied. *P<0.05; **P<0.01; ***P<0.001 versus untreated seedlings or versus treated wild-type seedlings when indicated by brackets.
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pone-0041327-g004: Effects of exogenous IAA and ACC on ataucsia-1 root growth.(A) Root phenotype of 10 days old wild-type and ataucsia-1 seedlings after treatment with IAA (0.03 and 0.1 µM). (B) Quantification of IAA effect on root growth. Seeds of wild-type and ataucsia-1 were germinated on nutrient medium for 5 days and then transferred to new medium either supplemented or not supplemented with IAA (0, 0.03 and 0.1 µM). Five days later, new root growth was evaluated. (Left) New primary root growth was measured and plotted as percentage of root growth on medium without IAA. (Right) Weight of root apparatus per cm of primary root length. (C) Quantification of ACC effect on root growth. As performed for panel B, 5 days old seedlings were transferred to medium supplemented or not with ACC (0, and 1 µM). Five days later, root growth was evaluated. (Left) Primary root growth. (Right) Two sets of y-axes are reported, on the left y-axis the weight of root apparatus per cm of primary root length and on the right y-axis the density of emerged lateral roots (number of lateral roots per cm of primary root). The values reported in B and C are means ± SE (n = 3) 15–20 seedlings per replicate. Student's t-test was applied. *P<0.05; **P<0.01; ***P<0.001 versus untreated seedlings or versus treated wild-type seedlings when indicated by brackets.

Mentions: Both acropetal and basipetal auxin transport systems are crucial for lateral root development [40]. Since ataucsia-1 mutants are impaired in PAT as compared with wild-type, we investigated the effect of ataucsia-1 mutation on primary and lateral root growth in the presence or absence of exogenous auxin. Primary root growth and lateral root initiation and elongation can be stimulated or inhibited by exogenous auxin depending on the concentration [10], [41]. 5-day-old seedlings were treated with 0.03 and 0.1 µM indole-3-acetic acid (IAA). As already reported [41], these concentrations had inhibitory effects on primary root growth. The effect of IAA on primary root growth was similar in ataucsia-1 mutant (SALK_ 117986) and wild-type seedlings (Figure 4A and 4B). At the IAA concentrations tested, lateral root growth (evaluated as weight of root apparatus per cm of primary root length [42]) was enhanced in wild-type plants (Figure 4B), but ataucsia-1 mutant displayed a more pronounced increase in lateral root growth at both 0.03 and 0.1 µM IAA concentrations (Figure 4B). On the other hand, the lateral root density (calculated as number of lateral roots per cm of primary root excluding the distal region not forming the lateral roots) in auxin-treated ataucsia-1 mutant and wild-type seedlings did not differ. These data indicate that the promoting effect of IAA on lateral root growth is enhanced in ataucsia-1 mutant, whereas auxin-regulated lateral root initiation is unaffected.


Arabidopsis thaliana AUCSIA-1 regulates auxin biology and physically interacts with a kinesin-related protein.

Molesini B, Pandolfini T, Pii Y, Korte A, Spena A - PLoS ONE (2012)

Effects of exogenous IAA and ACC on ataucsia-1 root growth.(A) Root phenotype of 10 days old wild-type and ataucsia-1 seedlings after treatment with IAA (0.03 and 0.1 µM). (B) Quantification of IAA effect on root growth. Seeds of wild-type and ataucsia-1 were germinated on nutrient medium for 5 days and then transferred to new medium either supplemented or not supplemented with IAA (0, 0.03 and 0.1 µM). Five days later, new root growth was evaluated. (Left) New primary root growth was measured and plotted as percentage of root growth on medium without IAA. (Right) Weight of root apparatus per cm of primary root length. (C) Quantification of ACC effect on root growth. As performed for panel B, 5 days old seedlings were transferred to medium supplemented or not with ACC (0, and 1 µM). Five days later, root growth was evaluated. (Left) Primary root growth. (Right) Two sets of y-axes are reported, on the left y-axis the weight of root apparatus per cm of primary root length and on the right y-axis the density of emerged lateral roots (number of lateral roots per cm of primary root). The values reported in B and C are means ± SE (n = 3) 15–20 seedlings per replicate. Student's t-test was applied. *P<0.05; **P<0.01; ***P<0.001 versus untreated seedlings or versus treated wild-type seedlings when indicated by brackets.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3401106&req=5

pone-0041327-g004: Effects of exogenous IAA and ACC on ataucsia-1 root growth.(A) Root phenotype of 10 days old wild-type and ataucsia-1 seedlings after treatment with IAA (0.03 and 0.1 µM). (B) Quantification of IAA effect on root growth. Seeds of wild-type and ataucsia-1 were germinated on nutrient medium for 5 days and then transferred to new medium either supplemented or not supplemented with IAA (0, 0.03 and 0.1 µM). Five days later, new root growth was evaluated. (Left) New primary root growth was measured and plotted as percentage of root growth on medium without IAA. (Right) Weight of root apparatus per cm of primary root length. (C) Quantification of ACC effect on root growth. As performed for panel B, 5 days old seedlings were transferred to medium supplemented or not with ACC (0, and 1 µM). Five days later, root growth was evaluated. (Left) Primary root growth. (Right) Two sets of y-axes are reported, on the left y-axis the weight of root apparatus per cm of primary root length and on the right y-axis the density of emerged lateral roots (number of lateral roots per cm of primary root). The values reported in B and C are means ± SE (n = 3) 15–20 seedlings per replicate. Student's t-test was applied. *P<0.05; **P<0.01; ***P<0.001 versus untreated seedlings or versus treated wild-type seedlings when indicated by brackets.
Mentions: Both acropetal and basipetal auxin transport systems are crucial for lateral root development [40]. Since ataucsia-1 mutants are impaired in PAT as compared with wild-type, we investigated the effect of ataucsia-1 mutation on primary and lateral root growth in the presence or absence of exogenous auxin. Primary root growth and lateral root initiation and elongation can be stimulated or inhibited by exogenous auxin depending on the concentration [10], [41]. 5-day-old seedlings were treated with 0.03 and 0.1 µM indole-3-acetic acid (IAA). As already reported [41], these concentrations had inhibitory effects on primary root growth. The effect of IAA on primary root growth was similar in ataucsia-1 mutant (SALK_ 117986) and wild-type seedlings (Figure 4A and 4B). At the IAA concentrations tested, lateral root growth (evaluated as weight of root apparatus per cm of primary root length [42]) was enhanced in wild-type plants (Figure 4B), but ataucsia-1 mutant displayed a more pronounced increase in lateral root growth at both 0.03 and 0.1 µM IAA concentrations (Figure 4B). On the other hand, the lateral root density (calculated as number of lateral roots per cm of primary root excluding the distal region not forming the lateral roots) in auxin-treated ataucsia-1 mutant and wild-type seedlings did not differ. These data indicate that the promoting effect of IAA on lateral root growth is enhanced in ataucsia-1 mutant, whereas auxin-regulated lateral root initiation is unaffected.

Bottom Line: Two allelic mutants for AtAucsia-1 gene did not display visible root morphological alterations; however both basipetal and acropetal indole-3-acetic acid (IAA) root transport was reduced as compared with wild-type plants.The transcript steady state levels of the auxin efflux transporters ATP BINDING CASSETTE subfamily B (ABCB) ABCB1, ABCB4 and ABCB19 were reduced in ataucsia-1 plants.Gene ontology predictions for the two proteins are consistent with the hypothesis that the AtAUCSIA-1/AtAUCSIA-1IP complex is involved in the regulation of the cytoskeleton dynamics underlying auxin biology.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, University of Verona, Verona, Italy.

ABSTRACT
Aucsia is a green plant gene family encoding 44-54 amino acids long miniproteins. The sequenced genomes of most land plants contain two Aucsia genes. RNA interference of both tomato (Solanum lycopersicum) Aucsia genes (SlAucsia-1 and SlAucsia-2) altered auxin sensitivity, auxin transport and distribution; it caused parthenocarpic development of the fruit and other auxin-related morphological changes. Here we present data showing that the Aucsia-1 gene of Arabidopsis thaliana alters, by itself, root auxin biology and that the AtAUCSIA-1 miniprotein physically interacts with a kinesin-related protein. The AtAucsia-1 gene is ubiquitously expressed, although its expression is higher in roots and inflorescences in comparison to stems and leaves. Two allelic mutants for AtAucsia-1 gene did not display visible root morphological alterations; however both basipetal and acropetal indole-3-acetic acid (IAA) root transport was reduced as compared with wild-type plants. The transcript steady state levels of the auxin efflux transporters ATP BINDING CASSETTE subfamily B (ABCB) ABCB1, ABCB4 and ABCB19 were reduced in ataucsia-1 plants. In ataucsia-1 mutant, lateral root growth showed an altered response to i) exogenous auxin, ii) an inhibitor of polar auxin transport and iii) ethylene. Overexpression of AtAucsia-1 inhibited primary root growth. In vitro and in vivo protein-protein interaction experiments showed that AtAUCSIA-1 interacts with a 185 amino acids long fragment belonging to a 2712 amino acids long protein of unknown function (At4g31570). Bioinformatics analysis indicates that the AtAUCSIA-1 interacting protein (AtAUCSIA-1IP) clusters with a group of CENP-E kinesin-related proteins. Gene ontology predictions for the two proteins are consistent with the hypothesis that the AtAUCSIA-1/AtAUCSIA-1IP complex is involved in the regulation of the cytoskeleton dynamics underlying auxin biology.

Show MeSH