Co‐expression of Arabidopsis transcription factor, AtMYB12, and soybean isoflavone synthase, GmIFS1, genes in tobacco leads to enhanced biosynthesis of isoflavones and flavonols resulting in osteoprotective activity

Abstract

SummaryIsoflavones, a group of flavonoids, restricted almost exclusively to family Leguminosae are known to exhibit anticancerous and anti-osteoporotic activities in animal systems and have been a target for metabolic engineering in commonly consumed food crops. Earlier efforts based on the expression of legume isoflavone synthase (IFS) genes in nonlegume plant species led to the limited success in terms of isoflavone content in transgenic tissue due to the limitation of substrate for IFS enzyme. In this work to overcome this limitation, the activation of multiple genes of flavonoid pathway using Arabidopsis transcription factor AtMYB12 has been carried out. We developed transgenic tobacco lines constitutively co-expressing AtMYB12 and GmIFS1 (soybean IFS) genes or independently and carried out their phytochemical and molecular analyses. The leaves of co-expressing transgenic lines were found to have elevated flavonol content along with the accumulation of substantial amount of genistein glycoconjugates being at the highest levels that could be engineered in tobacco leaves till date. Oestrogen-deficient (ovariectomized, Ovx) mice fed with leaf extract from transgenic plant co-expressing AtMYB12 and GmIFS1 but not wild-type extract exhibited significant conservation of trabecular microarchitecture, reduced osteoclast number and expression of osteoclastogenic genes, higher total serum antioxidant levels and increased uterine oestrogenicity compared with Ovx mice treated with vehicle (control). The skeletal effect of the transgenic extract was comparable to oestrogen-treated Ovx mice. Together, our results establish an efficient strategy for successful pathway engineering of isoflavones and other flavonoids in crop plants and provide a direct evidence of improved osteoprotective effect of transgenic plant extract.

Gene regulation of anthocyanin biosynthesis in two blood-flesh peach (Prunus persica (L.) Batsch) cultivars during fruit development

“…Anthocyanins synthesized by the phenylpropanoid pathway have been well characterized in different plant species (Pandey et al, 2014). The major anthocyanins include pelargonidin (orange or red), cyanidin (pink or red), and delphinidin (purple or blue) and their formation depends on their hydroxylation pattern (Niu et al, 2010).…”

MicroRNA858 Is a Potential Regulator of Phenylpropanoid Pathway and Plant Development

“…The flavonol-specific MYBs induced the expression of structural genes such as CHS, CHI, F3H, and FLS1 of the phenylpropanoid pathway (Stracke et al, 2007;Dubos et al, 2010;Xu et al, 2015). Previously, a plethora of reports suggested that the expression of such MYBs in tobacco (Nicotiana tabacum) and tomato enhances the expression of structural genes of the pathway leading to enhanced flavonoid content, nutritional quality, and insect resistance (Luo et al, 2008;Misra et al, 2010;Pandey et al, 2012Pandey et al, , 2014aPandey et al, , 2014bPandey et al, , 2015aPandey et al, , 2015bChoudhary et al, 2016). Here, we describe the participation of miR858a in the transcription factor regulon responsible for the biosynthesis of flavonoids and development in Arabidopsis.…”

Transcriptional regulators of flavonoid biosynthesis and their application to flower color modification in Japanese gentians

“…The transgenic tobacco flowers show decreased anthocyanin levels compared with flowers overexpressing PAP1 alone. In other instances, coexpression of Arabidopsis AtMYB12 and the soybean isoflavone synthase gene can lead to enhanced biosynthesis of isoflavones and flavonols both in leaves and petals (Pandey et al 2014). For the future, the combination of transcription factors and structural genes is a more attractive approach for the engineering of specific metabolic flow and the creation of novel flower colors and patterns.…”