Enhanced Virulence Gene Activity of Agrobacterium in Muskmelon (Cucumis melo L.) cv. ‘Birdie’

Abstract

Muskmelon (Cucumis melo L.) cultivar 'Birdie' , was evaluated for its response to the tumorigenic Agrobacterium tumefaciens and the oncogenic A. rhizogenes strains. Stem and petiole of three week-old in vitro-grown muskmelon plants were inoculated with five strains of A. tumefaciens and A. rhizogenes each and observed phenotypic expressions i.e. induction of crown galls and hairy roots. This phenotypic expression was efficaciously increased when virulence gene activity of different strains of two Agrobacterium species was enhanced. Intensive studies on enhancement of virulence gene activity of Agrobacterium found to be correlated to the appropriate light intensity (39.3 µmol m -2 s -1) with a specific concentration of monocyclic phenolic compound, acetosyringone (20 µM). The gene activity was also influenced by several other physical factors e.g. plant tissue type, Agrobacterium species and their strains, and plant tissue-Agrobacterium interaction. Among the different A. tumefaciens strains, LBA4404 showed the best virulence gene activity in both stem and petiole through the formation of higher rate of crown galls. On the other hand, strain 15834 of A. rhizogenes showed better gene activity in stem and 8196 in petiole through the formation of higher rate of hairy roots as well as higher average number of hairy roots. Among the two different types of explants, petiole was more susceptible to both Agrobacterium species. Thus it was concluded that future muskmelon transformation study can efficiently be carried out with LBA4404, 15834 and 8196 strains using petiole explants by adding 20 µM of acetosyringone in the medium.

Elite hairy roots of Raphanus sativus (L.) as a source of antioxidants and flavonoids

“…Acetosyringone, a monocyclic phenolic compound, plays an important role on vir gene activation and T-DNA transfer (Ridgway et al 2004). Mohiuddin et al (2011) reported that acetosyringone, an amino acid derivative, is essential for biological activity and maintenance of vir gene expression in host cells. Recently, Srinivasan et al (2014) reported that carrot transformation efficiency of MTCC 2364 and MTCC 532 was highly dependent on the acetosyringone concentration.…”

An Optimized Protocol for Agrobacterium rhizogenes-Mediated Genetic Transformation of Citrullus colocynthis

“…13,19 The effect that Agrobacterium strain and the type of explant had on the transformation efficiency of cucurbits was well documented. [20][21][22] To achieve an optimized condition for the establishment, virulence of four Agrobacterium strains (MSU440, A4, A13, ACTT 15834) were compared against three types of colocynth explants (leaf, excised shoot and hypocotyl). According to the results (Figure 1), all the studied strains were virulent against the leaf and excised shoot explants.…”

“…28 This compound also increased the virulence of the strains ACTT 15834 and 8196 on Muskmelon (Cucumis melo). 22…”

Induction of hairy roots and plant regeneration from the medicinal plant Pogostemon Cablin

“…AS is an amino acid derivative and a phenolic compound, which must be constant for biological activity and maintenance of vir gene expression in Muskmelon explants. 23 Many other reports also pointed out that the vir genes are inducible in response to the monocyclic phenolic compound like AS. 24 The results obtained from higher (20 mg l-1) concentration of AS indicated an inhibitory action rather than stimulatory.…”