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Change in auxin and cytokinin levels coincides with altered expression of branching genes during axillary bud outgrowth in Chrysanthemum

(2016) PLOS ONE. 11(8).
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Abstract
In the production and breeding of Chrysanthemum sp., shoot branching is an important quality aspect as the outgrowth of axillary buds determines the final plant shape. Bud outgrowth is mainly controlled by apical dominance and the crosstalk between the plant hormones auxin, cytokinin and strigolactone. In this work the hormonal and genetic regulation of axillary bud outgrowth was studied in two differently branching cut flower Chrysanthemum morifolium (Ramat) genotypes. C17 is a split-type which forms an inflorescence meristem after a certain vegetative period, while C18 remains vegetative under long day conditions. Plant growth of both genotypes was monitored during 5 subsequent weeks starting one week before flower initiation occurred in C17. Axillary bud outgrowth was measured weekly and samples of shoot apex, stem and axillary buds were taken during the first two weeks. We combined auxin and cytokinin measurements by UPLC-MS/MS with RT-qPCR expression analysis of genes involved in shoot branching regulation pathways in chrysanthemum. These included bud development genes (CmBRC1, CmDRM1, CmSTM, CmLsL), auxin pathway genes (CmPIN1, CmTIR3, CmTIR1, CmAXR1, CmAXR6, CmAXR2, CmIAA16, CmIAA12), cytokinin pathway genes (CmIPT3, CmHK3, CmRR1) and strigolactone genes (CmMAX1 and CmMAX2). Genotype C17 showed a release from apical dominance after floral transition coinciding with decreased auxin and increased cytokinin levels in the subapical axillary buds. As opposed to C17, C18 maintained strong apical dominance with vegetative growth throughout the experiment. Here high auxin levels and decreasing cytokinin levels in axillary buds and stem were measured. A differential expression of several branching genes accompanied the different hormonal change and bud outgrowth in C17 and C18. This was clear for the strigolactone biosynthesis gene CmMAX1, the transcription factor CmBRC1 and the dormancy associated gene CmDRM1, that all showed a decreased expression in C17 at floral transition and an increased expression in C18 with continuous vegetative growth. These results offer a case study for Chrysanthemum, showing an altered cytokinin to auxin balance and differential gene expression between vegetative growth with apical dominance and transition to generative growth with loss of apical dominance and axillary bud outgrowth. This suggests a conservation of several aspects of the hormonal and genetical regulation of bud outgrowth in Chrysanthemum. Furthermore, 15 previously uncharacterised genes in chrysanthemum, were described in this study. Of those genes involved in axillary bud outgrowth we identified CmDRM1, CmBRC1 and CmMAX1 as having an altered expression preceding axillary bud outgrowth, which could be useful as markers for bud activity.
Keywords
PEA, GROWTH, TRANSPORT, SHOOT, PLANT DEVELOPMENT, DENDRANTHEMA-GRANDIFLORUM, STRIGOLACTONE BIOSYNTHESIS, ACTS DOWNSTREAM, APICAL DOMINANCE, ARABIDOPSIS-THALIANA

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Citation

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Chicago
Dierck, Robrecht, Ellen De Keyser, Jan De Riek, Emmy Dhooghe, Johan Van Huylenbroeck, Els Prinsen, and Dominique Van Der Straeten. 2016. “Change in Auxin and Cytokinin Levels Coincides with Altered Expression of Branching Genes During Axillary Bud Outgrowth in Chrysanthemum.” Plos One 11 (8).
APA
Dierck, Robrecht, De Keyser, E., De Riek, J., Dhooghe, E., Van Huylenbroeck, J., Prinsen, E., & Van Der Straeten, D. (2016). Change in auxin and cytokinin levels coincides with altered expression of branching genes during axillary bud outgrowth in Chrysanthemum. PLOS ONE, 11(8).
Vancouver
1.
Dierck R, De Keyser E, De Riek J, Dhooghe E, Van Huylenbroeck J, Prinsen E, et al. Change in auxin and cytokinin levels coincides with altered expression of branching genes during axillary bud outgrowth in Chrysanthemum. PLOS ONE. 2016;11(8).
MLA
Dierck, Robrecht, Ellen De Keyser, Jan De Riek, et al. “Change in Auxin and Cytokinin Levels Coincides with Altered Expression of Branching Genes During Axillary Bud Outgrowth in Chrysanthemum.” PLOS ONE 11.8 (2016): n. pag. Print.
@article{8197209,
  abstract     = {In the production and breeding of Chrysanthemum sp., shoot branching is an important quality aspect as the outgrowth of axillary buds determines the final plant shape. Bud outgrowth is mainly controlled by apical dominance and the crosstalk between the plant hormones auxin, cytokinin and strigolactone. In this work the hormonal and genetic regulation of axillary bud outgrowth was studied in two differently branching cut flower Chrysanthemum morifolium (Ramat) genotypes. C17 is a split-type which forms an inflorescence meristem after a certain vegetative period, while C18 remains vegetative under long day conditions. Plant growth of both genotypes was monitored during 5 subsequent weeks starting one week before flower initiation occurred in C17. Axillary bud outgrowth was measured weekly and samples of shoot apex, stem and axillary buds were taken during the first two weeks. We combined auxin and cytokinin measurements by UPLC-MS/MS with RT-qPCR expression analysis of genes involved in shoot branching regulation pathways in chrysanthemum. These included bud development genes (CmBRC1, CmDRM1, CmSTM, CmLsL), auxin pathway genes (CmPIN1, CmTIR3, CmTIR1, CmAXR1, CmAXR6, CmAXR2, CmIAA16, CmIAA12), cytokinin pathway genes (CmIPT3, CmHK3, CmRR1) and strigolactone genes (CmMAX1 and CmMAX2). Genotype C17 showed a release from apical dominance after floral transition coinciding with decreased auxin and increased cytokinin levels in the subapical axillary buds. As opposed to C17, C18 maintained strong apical dominance with vegetative growth throughout the experiment. Here high auxin levels and decreasing cytokinin levels in axillary buds and stem were measured. A differential expression of several branching genes accompanied the different hormonal change and bud outgrowth in C17 and C18. This was clear for the strigolactone biosynthesis gene CmMAX1, the transcription factor CmBRC1 and the dormancy associated gene CmDRM1, that all showed a decreased expression in C17 at floral transition and an increased expression in C18 with continuous vegetative growth. These results offer a case study for Chrysanthemum, showing an altered cytokinin to auxin balance and differential gene expression between vegetative growth with apical dominance and transition to generative growth with loss of apical dominance and axillary bud outgrowth. This suggests a conservation of several aspects of the hormonal and genetical regulation of bud outgrowth in Chrysanthemum. Furthermore, 15 previously uncharacterised genes in chrysanthemum, were described in this study. Of those genes involved in axillary bud outgrowth we identified CmDRM1, CmBRC1 and CmMAX1 as having an altered expression preceding axillary bud outgrowth, which could be useful as markers for bud activity.},
  articleno    = {e0161732},
  author       = {Dierck, Robrecht and De Keyser, Ellen and De Riek, Jan  and Dhooghe, Emmy and Van Huylenbroeck, Johan and Prinsen, Els and Van Der Straeten, Dominique},
  issn         = {1932-6203},
  journal      = {PLOS ONE},
  keyword      = {PEA,GROWTH,TRANSPORT,SHOOT,PLANT DEVELOPMENT,DENDRANTHEMA-GRANDIFLORUM,STRIGOLACTONE BIOSYNTHESIS,ACTS DOWNSTREAM,APICAL DOMINANCE,ARABIDOPSIS-THALIANA},
  language     = {eng},
  number       = {8},
  pages        = {30},
  title        = {Change in auxin and cytokinin levels coincides with altered expression of branching genes during axillary bud outgrowth in Chrysanthemum},
  url          = {http://dx.doi.org/10.1371/journal.pone.0161732},
  volume       = {11},
  year         = {2016},
}

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