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Article|01 Sep 2021|OPEN
Auxin response and transport during induction of pedicel abscission in tomato
Xiufen Dong1,2, Chao Ma2,3, Tao Xu1, Cai-Zhong Jiang4,2,, Michael S. Reid2, & Tianlai Li1,
1Department of Horticulture, Shenyang Agricultural University, Shenyang 110866, China
2Department of Plant Sciences, University of California, Davis, CA 95616, USA
3Department of Ornamental Horticulture, College of Horticulture, China Agricultural University, Beijing 100193, China
4Crops Pathology & Genetic Research Unit, USDA-ARS, Davis, CA 95616, USA

Horticulture Research 8,
Article number: 192 (2021)
doi: 10.1038/hortres.2021.192
Views: 40

Received: 03 Feb 2021
Revised: 07 Jun 2021
Accepted: 07 Jun 2021
Published online: 01 Sep 2021

Abstract

Auxin plays a central role in control of organ abscission, and it is thought that changes in the auxin gradient across the abscission zone are the primary determinant of the onset of abscission. The nature of this gradient, whether in concentration, flow, or perhaps in the response system has not conclusively been determined. We employed a DR5::GUS auxin response reporter system to examine the temporal and spatial distribution of the auxin response activity in response to developmental and environmental cues during pedicel abscission in tomato. In pedicels of young and fully open flowers, auxin response, as indicated by GUS activity, was predominantly detected in the vascular tissues and was almost entirely confined to the abscission zone (AZ) and to the distal portion of the pedicel, with a striking reduction in the proximal tissues below the AZ—a ‘step’, rather than a gradient. Following pollination and during early fruit development, auxin response increased substantially throughout the pedicel. Changes in GUS activity following treatments that caused pedicel abscission (flower removal, high temperature, darkness, ethylene, or N-1-naphthylphthalamic acid (NPA) treatment) were relatively minor, with reduced auxin response in the AZ and some reduction above and below it. Expression of genes encoding some auxin efflux carriers (PIN) and influx carriers (AUX⁄LAX) was substantially reduced in the abscission zone of NPA-treated pedicels, and in pedicels stimulated to abscise by flower removal. Our results suggest that changes in auxin flow distribution through the abscission zone are likely more important than the auxin response system in the regulation of abscission.