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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.


Related in: MedlinePlus

Presence of CmF-308 transcript in the stems and apices of N. benthamiana plants 48 h after agroinfiltration of source leaves with plasmid containing the coding sequence of this transcript, indicating long-distance movement of the transcript (A). Absence of the gfp transcript from the apices and stems and presence of the transcript in the agroinfiltrated leaf (B). (C) Presence of the agrobacterium in the infected leaf 48 h after agroinfiltration. C, negative control RT-PCR with no cDNA template. (D) Picture of the infiltrated N. benthamiana plant.
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Figure 2: Presence of CmF-308 transcript in the stems and apices of N. benthamiana plants 48 h after agroinfiltration of source leaves with plasmid containing the coding sequence of this transcript, indicating long-distance movement of the transcript (A). Absence of the gfp transcript from the apices and stems and presence of the transcript in the agroinfiltrated leaf (B). (C) Presence of the agrobacterium in the infected leaf 48 h after agroinfiltration. C, negative control RT-PCR with no cDNA template. (D) Picture of the infiltrated N. benthamiana plant.

Mentions: As indicated, F-308 codes for Aux/IAA, one of the auxin-response regulators. The next set of experiments was aimed at studying the potential functioning of this gene product in the phloem, as a component of the auxin response pathway. A cassette harboring the coding sequence of CmF-308 under the AtSUC2 promoter was agroinfiltrated into leaves of N. benthamiana plants (Figure 2D). Presence of the melon transcript in the apices of these N. benthamiana plants 48 h post-infiltration established that this transcript is indeed capable of long-distance movement (Figure 2A). It is important to note that the gfp transcript that served as a control was absent from the stem and shoot apices, indicating that long-distance movement of RNA molecules is not a general phenomenon (Figure 2B). PCR analysis failed to detect segments of the binary plasmid, inserted into the Agrobacterium, outside the infiltrated leaf, indicating that the bacteria were restricted to this tissue during the first 48 h post-infiltration (Figure 2C).


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)

Presence of CmF-308 transcript in the stems and apices of N. benthamiana plants 48 h after agroinfiltration of source leaves with plasmid containing the coding sequence of this transcript, indicating long-distance movement of the transcript (A). Absence of the gfp transcript from the apices and stems and presence of the transcript in the agroinfiltrated leaf (B). (C) Presence of the agrobacterium in the infected leaf 48 h after agroinfiltration. C, negative control RT-PCR with no cDNA template. (D) Picture of the infiltrated N. benthamiana plant.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Presence of CmF-308 transcript in the stems and apices of N. benthamiana plants 48 h after agroinfiltration of source leaves with plasmid containing the coding sequence of this transcript, indicating long-distance movement of the transcript (A). Absence of the gfp transcript from the apices and stems and presence of the transcript in the agroinfiltrated leaf (B). (C) Presence of the agrobacterium in the infected leaf 48 h after agroinfiltration. C, negative control RT-PCR with no cDNA template. (D) Picture of the infiltrated N. benthamiana plant.
Mentions: As indicated, F-308 codes for Aux/IAA, one of the auxin-response regulators. The next set of experiments was aimed at studying the potential functioning of this gene product in the phloem, as a component of the auxin response pathway. A cassette harboring the coding sequence of CmF-308 under the AtSUC2 promoter was agroinfiltrated into leaves of N. benthamiana plants (Figure 2D). Presence of the melon transcript in the apices of these N. benthamiana plants 48 h post-infiltration established that this transcript is indeed capable of long-distance movement (Figure 2A). It is important to note that the gfp transcript that served as a control was absent from the stem and shoot apices, indicating that long-distance movement of RNA molecules is not a general phenomenon (Figure 2B). PCR analysis failed to detect segments of the binary plasmid, inserted into the Agrobacterium, outside the infiltrated leaf, indicating that the bacteria were restricted to this tissue during the first 48 h post-infiltration (Figure 2C).

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.


Related in: MedlinePlus