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Phloem-specific expression of a melon Aux/IAA in tomato plants alters auxin sensitivity and plant development.

Golan G, Betzer R, Wolf S - Front Plant Sci (2013)

Bottom Line: A similar effect on root development was obtained after transient expression of CmF-308 in source leaves of N. benthamiana plants.In addition to the altered root development, phloem-specific expression of CmF-308 resulted in shorter plants, a higher number of lateral shoots and delayed flowering, a phenotype resembling reduced apical dominance.The reduced auxin sensitivity in the shoot tissue was confirmed by lower relative expression of several Aux/IAA genes in leaves and an increase in the relative expression of a cytokinin-response regulator, TRR8/9b.

View Article: PubMed Central - PubMed

Affiliation: The Robert H. Smith Faculty of Agriculture, Food and Environment, Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem Rehovot, Israel.

ABSTRACT
Phloem sap contains a large repertoire of macromolecules in addition to sugars, amino acids, growth substances and ions. The transcription profile of melon phloem sap contains over 1000 mRNA molecules, most of them associated with signal transduction, transcriptional control, and stress and defense responses. Heterografting experiments have established the long-distance trafficking of numerous mRNA molecules. Interestingly, several trafficking transcripts are involved in the auxin response, including two molecules coding for auxin/indole acetic acid (Aux/IAA). To further explore the biological role of the melon Aux/IAA transcript CmF-308 in the vascular tissue, a cassette containing the coding sequence of this gene under a phloem-specific promoter was introduced into tomato plants. The number of lateral roots was significantly higher in transgenic plants expressing CmF-308 under the AtSUC2 promoter than in controls. A similar effect on root development was obtained after transient expression of CmF-308 in source leaves of N. benthamiana plants. An auxin-response assay showed that CmF-308-transgenic roots are more sensitive to auxin than control roots. In addition to the altered root development, phloem-specific expression of CmF-308 resulted in shorter plants, a higher number of lateral shoots and delayed flowering, a phenotype resembling reduced apical dominance. In contrast to the root response, cotyledons of the transgenic plants were less sensitive to auxin than control cotyledons. The reduced auxin sensitivity in the shoot tissue was confirmed by lower relative expression of several Aux/IAA genes in leaves and an increase in the relative expression of a cytokinin-response regulator, TRR8/9b. The accumulated data suggest that expression of Aux/IAA in the phloem modifies auxin sensitivity in a tissue-specific manner, thereby altering plant development.

No MeSH data available.


Effect of CmF-308 expression in the phloem of tomato plants on the expression of cytokinin-response genes. The expression of members of the tomato response regulator (TRR) gene family was determined by qRT-PCR in leaves (A) and roots (B) of 21-day-old CmF-308-transgenic (gray columns) and control M-82 (black columns) plants. Data represent means of four replications ± SE. Different letters indicate significant differences in relative expression of specific genes between the two plant lines at p < 0.05 by Student's t-test.
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Figure 9: Effect of CmF-308 expression in the phloem of tomato plants on the expression of cytokinin-response genes. The expression of members of the tomato response regulator (TRR) gene family was determined by qRT-PCR in leaves (A) and roots (B) of 21-day-old CmF-308-transgenic (gray columns) and control M-82 (black columns) plants. Data represent means of four replications ± SE. Different letters indicate significant differences in relative expression of specific genes between the two plant lines at p < 0.05 by Student's t-test.

Mentions: Further study was aimed at verifying the interaction between expression of auxin- and cytokinin-responsive genes (Figure 9). Relative expression of four cytokinin-induced Type A-tomato response regulators (TRRs) was similar in roots of CmF-308-transgenic and control plants (Figure 9B). However, relative expression of TRR8/9b was almost five times higher in leaves of CmF-308 vs. control plants (Figure 9A), suggesting a higher cytokinin response associated with the observed reduced auxin response.


Phloem-specific expression of a melon Aux/IAA in tomato plants alters auxin sensitivity and plant development.

Golan G, Betzer R, Wolf S - Front Plant Sci (2013)

Effect of CmF-308 expression in the phloem of tomato plants on the expression of cytokinin-response genes. The expression of members of the tomato response regulator (TRR) gene family was determined by qRT-PCR in leaves (A) and roots (B) of 21-day-old CmF-308-transgenic (gray columns) and control M-82 (black columns) plants. Data represent means of four replications ± SE. Different letters indicate significant differences in relative expression of specific genes between the two plant lines at p < 0.05 by Student's t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750518&req=5

Figure 9: Effect of CmF-308 expression in the phloem of tomato plants on the expression of cytokinin-response genes. The expression of members of the tomato response regulator (TRR) gene family was determined by qRT-PCR in leaves (A) and roots (B) of 21-day-old CmF-308-transgenic (gray columns) and control M-82 (black columns) plants. Data represent means of four replications ± SE. Different letters indicate significant differences in relative expression of specific genes between the two plant lines at p < 0.05 by Student's t-test.
Mentions: Further study was aimed at verifying the interaction between expression of auxin- and cytokinin-responsive genes (Figure 9). Relative expression of four cytokinin-induced Type A-tomato response regulators (TRRs) was similar in roots of CmF-308-transgenic and control plants (Figure 9B). However, relative expression of TRR8/9b was almost five times higher in leaves of CmF-308 vs. control plants (Figure 9A), suggesting a higher cytokinin response associated with the observed reduced auxin response.

Bottom Line: A similar effect on root development was obtained after transient expression of CmF-308 in source leaves of N. benthamiana plants.In addition to the altered root development, phloem-specific expression of CmF-308 resulted in shorter plants, a higher number of lateral shoots and delayed flowering, a phenotype resembling reduced apical dominance.The reduced auxin sensitivity in the shoot tissue was confirmed by lower relative expression of several Aux/IAA genes in leaves and an increase in the relative expression of a cytokinin-response regulator, TRR8/9b.

View Article: PubMed Central - PubMed

Affiliation: The Robert H. Smith Faculty of Agriculture, Food and Environment, Otto Warburg Minerva Center for Agricultural Biotechnology, The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem Rehovot, Israel.

ABSTRACT
Phloem sap contains a large repertoire of macromolecules in addition to sugars, amino acids, growth substances and ions. The transcription profile of melon phloem sap contains over 1000 mRNA molecules, most of them associated with signal transduction, transcriptional control, and stress and defense responses. Heterografting experiments have established the long-distance trafficking of numerous mRNA molecules. Interestingly, several trafficking transcripts are involved in the auxin response, including two molecules coding for auxin/indole acetic acid (Aux/IAA). To further explore the biological role of the melon Aux/IAA transcript CmF-308 in the vascular tissue, a cassette containing the coding sequence of this gene under a phloem-specific promoter was introduced into tomato plants. The number of lateral roots was significantly higher in transgenic plants expressing CmF-308 under the AtSUC2 promoter than in controls. A similar effect on root development was obtained after transient expression of CmF-308 in source leaves of N. benthamiana plants. An auxin-response assay showed that CmF-308-transgenic roots are more sensitive to auxin than control roots. In addition to the altered root development, phloem-specific expression of CmF-308 resulted in shorter plants, a higher number of lateral shoots and delayed flowering, a phenotype resembling reduced apical dominance. In contrast to the root response, cotyledons of the transgenic plants were less sensitive to auxin than control cotyledons. The reduced auxin sensitivity in the shoot tissue was confirmed by lower relative expression of several Aux/IAA genes in leaves and an increase in the relative expression of a cytokinin-response regulator, TRR8/9b. The accumulated data suggest that expression of Aux/IAA in the phloem modifies auxin sensitivity in a tissue-specific manner, thereby altering plant development.

No MeSH data available.