Attenuation of the Phenotype Caused by the Root-Inducing, Left-Hand, Transferred DNA and Its rolA Gene (Correlations with Changes in Polyamine Metabolism and DNA Methylation)

Abstract

We present four examples of attenuation of the transformed phenotype caused by the root-inducing, left-hand, transferred DNA from Agrobacterium rhizogenes in tobacco (Nicotiana tabacum). The first was associated with a genetic variable (homozygosity for the T-DNA), and the second was induced at the physiological level by putrescine and tyramine, suggesting that the transformed phenotype depends on defective polyamine metabolism. Physiological attenuation is further illustrated in the third example, i n which the inhibition of flowering caused by P,,,-ro/A, a gene from the rootinducing, left-hand, transferred DNA driven by a strong vira1 promoter, was attenuated by grafting the transformed shoot onto nontransformed rootstock that had been induced to flower. lnfertility in the resulting flowers was corrected by a mixture of putrescine and tyramine, indicating that P,,,-ro/A inhibited flowering through interference with polyamine conjugation and that tyramine was essentia1 to fertility. A fourth example of attenuation of the transformed phenotype occurred in lateral branches of plants expressing rolA under the control of its native promoter. In these branches, reduction in the accumulation of ro/A transcripts was correlated with the methylation of a site 3' to the rolA coding sequence; thus, the transformed plant seems capable of recognizing and repressing a gene that interferes with flowering.

Plant hybridization

“…Hybridization has also been reported to generate novel isozyme alleles (Woodruff, 1989), but this result may simply be an artifact of sampling error. Restriction fragment patterns are known to change because of different patterns of methylation in hybrids (Jablonka & Lamb, 1995 ;Song et al, 1995), and genes introduced through sexual hybridization or genetic engineering are often inactivated (Wallace & Landbridge, 1971 ;Martin-Tanguy et al, 1996). Perhaps the most serious problems arise from analyses of repetitive sequences in which concerted evolution can lead to the replacement or loss of alleles from one of the parental species (Arnold, Contreras & Shaw, 1988).…”

Wound-Inducible Biosynthesis of Phytoalexin Hydroxycinnamic Acid Amides of Tyramine in Tryptophan and Tyrosine Decarboxylase Transgenic Tobacco Lines

“…The biosynthesis of PCAAT is elicited by wounding (Pearce et al, 1998;Ishihara et al, 2000) or pathogen inoculation (Keller et al, 1996;Muhlenbeck et al, 1996;Schmidt et al, 1998;Newman et al, 2001) in many species (Martin-Tanguy et al, 1996), especially in solanaceous plants (Clarke, 1982;Keller et al, 1996;Muhlenbeck et al, 1996). PCAAT can be further integrated into cell walls via a peroxidase-mediated process (Negrel and Lherminier, 1987;Keller et al, 1996) that yields monoor dicovalent ether bonds between cinnamoyl or tyramine moieties of PCAAT and the plant phenolic cell wall matrix (Lapierre et al, 1996).…”

“…The immunolocalization of acyltransferase in the vascular tissues of opium poppy further corroborates the importance of PCAAT for cell wall cross-linking. On the other hand, an external supply of tyramine (0.5 mM) provided through watering solution or leaf spraying can significantly increase the levels of p-coumaroyltyramine (p-CT) or feruloyltyramine (FT) in leaf tissue of wild-type tobacco (Nicotiana tabacum; Martin-Tanguy et al, 1996) and rice plants transformed with a heterologous pepper hydroxycinnamoyltransferase (Jang et al, 2004). Altogether, these results indicate that modifications of aromatic amino acid pools or modifications of later steps may affect the biosynthesis and integration of phenolic compounds and/or PCAAT within the cell wall.…”

Agrobacterium rhizogenes-Mediated Transformation and Its Biotechnological Applications in Crops

“…Induced adventitious root formation by rolA, rolB and rolC genes is shown on tobacco, kalanchoe and tomato leaves (Cardarelli et al 1987a;Spena et al 1987;Spano et al 1988;van Altvorst et al 1992;Kiyokawa et al 1994) and plants carrying these genes are morphologically equivalent to those carrying the whole T L -DNA (Spano et al 1988). Inactivation or overexpression of various rol genes in stable transgenic lines or hairy-root cultures exhibits different variations in plant phenotypes and root morphology (Schmulling et al 1988;Martin-Tanguy et al 1996;Casanova et al 2004). …”