Branching gene expression during chrysanthemum axillary bud outgrowth regulated by strigolactone and auxin transport

Branching gene expression during chrysanthemum axillary bud outgrowth regulated by strigolactone... Shoot branching is essential in ornamental chrysanthemum production and determines final plant shape and quality. Auxin is associated with apical dominance to indirectly inhibit bud outgrowth. Two non-mutually exclusive models exist for indirect auxin inhibition. Basipetal auxin transport inhibits axillary bud outgrowth by limiting auxin export from buds to stem (canalization model) or by increasing strigolactone levels (second messenger model). Here we analyzed bud outgrowth in treatments with auxin (IAA), strigolactone (GR24) and auxin transport inhibitor (NPA) using a split-plate bioassay with isolated chrysanthemum stem segments. Besides measuring bud length, dividing cell percentage was measured with flow cytometry and RT-qPCR was used to monitor expression levels of genes involved in auxin transport (CmPIN1) and signaling (CmAXR2), bud dormancy (CmBRC1, CmDRM1) and strigolactone biosynthesis (CmMAX1, CmMAX3). Treatments over a 5-day period showed bud outgrowth in the control and inhibition with IAA and IAA + GR24. Bud outgrowth in the control coincided with high dividing cell percentage, decreased expression of CmBRC1 and CmDRM1 and increased CmPIN1 expression. Inhibition by IAA and IAA + GR24 coincided with low dividing cell percentage and unchanged or increased expressions of CmBRC1, CmDRM1 and CmPIN1. Treatment with GR24 showed restricted bud outgrowth that was counteracted by NPA. This restricted bud outgrowth was still concomitant with a high dividing cell percentage and coincided with decreased expression of dormancy genes. These results indicate incomplete inhibition of bud outgrowth by GR24 treatment and suggest involvement of auxin transport in the mechanism of bud inhibition by strigolactones, supporting the canalization model. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Growth Regulation Springer Journals

Branching gene expression during chrysanthemum axillary bud outgrowth regulated by strigolactone and auxin transport

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Publisher
Springer Netherlands
Copyright
Copyright © 2018 by Springer Science+Business Media B.V., part of Springer Nature
Subject
Life Sciences; Plant Sciences; Plant Anatomy/Development; Plant Physiology; Agriculture
ISSN
0167-6903
eISSN
1573-5087
D.O.I.
10.1007/s10725-018-0408-2
Publisher site
See Article on Publisher Site

Abstract

Shoot branching is essential in ornamental chrysanthemum production and determines final plant shape and quality. Auxin is associated with apical dominance to indirectly inhibit bud outgrowth. Two non-mutually exclusive models exist for indirect auxin inhibition. Basipetal auxin transport inhibits axillary bud outgrowth by limiting auxin export from buds to stem (canalization model) or by increasing strigolactone levels (second messenger model). Here we analyzed bud outgrowth in treatments with auxin (IAA), strigolactone (GR24) and auxin transport inhibitor (NPA) using a split-plate bioassay with isolated chrysanthemum stem segments. Besides measuring bud length, dividing cell percentage was measured with flow cytometry and RT-qPCR was used to monitor expression levels of genes involved in auxin transport (CmPIN1) and signaling (CmAXR2), bud dormancy (CmBRC1, CmDRM1) and strigolactone biosynthesis (CmMAX1, CmMAX3). Treatments over a 5-day period showed bud outgrowth in the control and inhibition with IAA and IAA + GR24. Bud outgrowth in the control coincided with high dividing cell percentage, decreased expression of CmBRC1 and CmDRM1 and increased CmPIN1 expression. Inhibition by IAA and IAA + GR24 coincided with low dividing cell percentage and unchanged or increased expressions of CmBRC1, CmDRM1 and CmPIN1. Treatment with GR24 showed restricted bud outgrowth that was counteracted by NPA. This restricted bud outgrowth was still concomitant with a high dividing cell percentage and coincided with decreased expression of dormancy genes. These results indicate incomplete inhibition of bud outgrowth by GR24 treatment and suggest involvement of auxin transport in the mechanism of bud inhibition by strigolactones, supporting the canalization model.

Journal

Plant Growth RegulationSpringer Journals

Published: Jun 5, 2018

References

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