Molecular physiology of adventitious root formation in Petunia hybrida cuttings: involvement of wound response and primary metabolism

Abstract

Summary• Adventitious root formation (ARF) in the model plant Petunia hybrida cv. Mitchell has been analysed in terms of anatomy, gene expression, enzymatic activities and levels of metabolites. This study focuses on the involvement of wound response and primary metabolism.• Microscopic techniques were complemented with targeted transcript, enzyme and metabolite profiling using real time polymerase chain reaction (PCR), Northern blot, enzymatic assays, chromatography and mass spectrometry.• Three days after severance from the stock plants, first meristematic cells appeared which further developed into root primordia and finally adventitious roots. Excision of cuttings led to a fast and transient increase in the wound-hormone jasmonic acid, followed by the expression of jasmonate-regulated genes such as cell wall invertase. Analysis of soluble and insoluble carbohydrates showed a continuous accumulation during ARF. A broad metabolite profiling revealed a strong increase in organic acids and resynthesis of essential amino acids.• Substantial changes in enzyme activities and metabolite levels indicate that specific enzymes and metabolites might play a crucial role during ARF. Three metabolic phases could be defined: (i) sink establishment phase characterized by apoplastic unloading of sucrose and being probably mediated by jasmonates; (ii) recovery phase; and (iii) maintenance phase, in which a symplastic unloading occurs.

Auxin Controls Arabidopsis Adventitious Root Initiation by Regulating Jasmonic Acid Homeostasis

“…The protein product of the gene GH3.11, which is also called JASMONIC ACID RESISTANT1 (JAR1), conjugates JA to Ile, producing jasmonoyl-L-isoleucine (JA-Ile), the active signaling molecule recognized by the F-box receptor CORONATINE INSENSITIVE1 (COI1) (Fonseca et al, 2009). In addition, methyl jasmonate was shown to inhibit root growth in Arabidopsis (Staswick et al, 1992), and JA transiently accumulated at the base of Petunia hybrida stem cuttings after mechanical wounding but very rapidly returned to its basal level before adventitious root formation took place (Ahkami et al, 2009). Fattorini et al (2009) showed that submicromolar amounts of methyl jasmonate promoted adventitious root development from thin cell layers of tobacco (Nicotiana tabacum).…”

Interspecific RNA Interference of SHOOT MERISTEMLESS-Like Disrupts Cuscuta pentagona Plant Parasitism

“…Ultrastructural analysis of the origin of adventitious roots in cuttings of the distant relative petunia (Petunia hybrida) show their origin from cell divisions within the cambium layer itself (Ahkami et al, 2009) in a manner distinct from the dedifferentiation of cortical parenchyma in dodder. At no point in the dodder life cycle does the plant possess a normal root.…”

Plant regeneration: cellular origins and molecular mechanisms

“…In Arabidopsis tissue culture where explants incubated on auxin-rich callus-inducing medium (CIM) were subsequently transferred on to cytokinin-rich shoot-inducing medium (SIM) (Valvekens et al, 1988), intact, uncut plants hardly regenerated shoots at all (Iwase et al, 2015), thus demonstrating a requirement for wound stimuli in initiating regeneration. Wounding induces numerous cellular responses, including the production of plant hormones (Ahkami et al, 2009), loss of cell-to-cell communication and disruption of long-distance signaling .…”