Auxin response and transport during induction of pedicel abscission in tomato

Xiufen Dong,Michael S Reid,Cai-Zhong Jiang,Tianlai Li,Chao Ma,Tao Xu

doi:10.1038/s41438-021-00626-8

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.

Highlights

Abscission is the process of organ separation, which plays a critical role in the plant life cycle[1,2]
Auxin is considered to be a key hormone in the initiation of abscission; the accepted model suggests that reduced transport of auxin through the abscission zone (AZ) results in sensitization of the AZ to ethylene, which induces the chain of hydrolytic and other processes that lead to cell separation[1,2,5,12,13]
Silencing KD1 increased auxin in the abscission zone, and microarray analysis suggested that this was associated with the downregulation of auxin efflux transporters, PIN9

Summary

Introduction

Abscission is the process of organ separation, which plays a critical role in the plant life cycle[1,2]. Organ shedding occurs at abscission zones (AZ), comprising small, densely cytoplasmic cells at the boundary between an organ and the main plant body[3,4]. Abscission has evolved as a successful strategy to adapt to the environment in response to developmental and environmental cues[5]. Abscission allows plants to detach nonfunctional or diseased organs and is important for seed dispersal[2,6]. The timing of abscission, especially of flower and fruit abscission, is of interest to agriculture[7]. Breeding of appropriate abscission behavior has successfully solved

Methods

Results

Conclusion