Grape berry ripening delay induced by a pre-veraison NAA treatment is paralleled by a shift in the expression pattern of auxin- and ethylene-related genes

摘要

Auxins act as repressors of ripening inception in grape (véraison), while ethylene and abscisic\udacid (ABA) play a positive role as inducers of the syndrome. Despite the increasing amount\udof information made available on this topic, the complex network of interactions among these\udhormones remains elusive. In order to shed light on these aspects, a holistic approach was\udadopted to evaluate, at the transcriptomic level, the crosstalk between hormones in grape\udberries, whose ripening progression was delayed by applying naphtalenacetic acid (NAA) one\udweek before véraison.\udResults\udThe NAA treatment caused significant changes in the transcription rate of about 1,500 genes,\udindicating that auxin delayed grape berry ripening also at the transcriptional level, along with\udthe recovery of a steady state of its intracellular concentration. Hormone indices analysis\udcarried out with the HORMONOMETER tool suggests that biologically active concentrations\udof auxins were achieved throughout a homeostatic recovery. This occurred within 7 days after\udthe treatment, during which the physiological response was mainly unspecific and due to a\udlikely pharmacological effect of NAA. This hypothesis is strongly supported by the upregulation\udof genes involved in auxin conjugation (GH3-like) and action (IAA4- and IAA31-\udlike). A strong antagonistic effect between auxin and ethylene was also observed, along with\uda substantial „synergism‟ between auxins and ABA, although to a lesser extent.\udConclusions\udThis study suggests that, in presence of altered levels of auxins, the crosstalk between\udhormones involves diverse mechanisms, acting at both the hormone response and\udbiosynthesis levels, creating a complex response network.