Enhanced Salt Stress Tolerance in Transgenic Potato Plants Expressing IbMYB1, a Sweet Potato Transcription Factor

Abstract

IbMYB1, a transcription factor (TF) for R2R3-type MYB TFs, is a key regulator of anthocyanin biosynthesis during storage of sweet potatoes. Anthocyanins provide important antioxidants of nutritional value to humans, and also protect plants from oxidative stress. This study aimed to increase transgenic potatoes' (Solanum tuberosum cv. LongShu No.3) tolerance to environmental stress and enhance their nutritional value. Transgenic potato plants expressing IbMYB1 genes under the control of an oxidative stress-inducible peroxidase (SWPA2) promoter (referred to as SM plants) were successfully generated through Agrobacterium-mediated transformation. Two representative transgenic SM5 and SM12 lines were evaluated for enhanced tolerance to salinity, UV-B rays, and drought conditions. Following treatment of 100 mM NaCl, seedlings of SM5 and SM12 lines showed less root damage and more shoot growth than control lines expressing only an empty vector. Transgenic potato plants in pots treated with 400 mM NaCl showed high amounts of secondary metabolites, including phenols, anthocyanins, and flavonoids, compared with control plants. After treatment of 400 mM NaCl, transgenic potato plants also showed high DDPH radical scavenging activity and high PS II photochemical efficiency compared with the control line. Furthermore, following treatment of NaCl, UV-B, and drought stress, the expression levels of IbMYB1 and several structural genes in the flavonoid biosynthesis such as CHS, DFR, and ANS in transgenic plants were found to be correlated with plant phenotype. The results suggest that enhanced IbMYB1 expression affects secondary metabolism, which leads to improved tolerance ability in transgenic potatoes.

A Scutellaria baicalensis R2R3-MYB gene, SbMYB8, regulates flavonoid biosynthesis and improves drought stress tolerance in transgenic tobacco

“…It was reported that in MYB-overexpressing transgenic Arabidopsis plants, the over-accumulation of anthocyanin was directly associated with oxidative and drought tolerance (Nakabayashi et al 2014). Transgenic potato plants overexpressing IbMYB1 showed high amounts of secondary metabolites, and had higher salt tolerance than non-transgenic plants (Cheng et al 2013). A few R2R3-MYB proteins, i.e.…”

“…Several wheat R2R3-MYBs, including TaMYB1 (Lee et al 2007), TaMYB2A (Mao et al 2011), TaMYB33 (Qin et al 2012, TaMYB73 ), TaMYB30-B (Zhang et al 2012a, were shown to improve stress tolerance in transgenic plants, respectively. MYB proteins were also reported to be involved in the flavonoid biosynthesis in many plant species (Cheng et al 2013).…”

Overexpression of snapdragon Delila (Del) gene in tobacco enhances anthocyanin accumulation and abiotic stress tolerance

“…Furthermore, flavonols are compounds with high antioxidant activity, and the upregulation of their biosynthesis increased protection against UV radiation in Ligustrum vulgare plants [16]. Potato plants overexpressing transcription factor IbMYB1 exhibited enhanced anthocyanin production and improved salinity tolerance [17]. Anthocyanin biosynthetic genes PAL and CHS are proposed as candidates for molecular breeding to increase crop resistance to wounding and salt stress [18].…”

Recent advances in potato genomics, transcriptomics, and transgenicsunder drought and heat stresses: a review

“…Transgenics preserved higher water content and had over twice the dry weight of NTs (Ahmad et al, 2008). In another study of the same group, COD-transformant potato plants showed higher antioxidant enzyme activity, better photosynthetic efficiency, higher chlorophyll content, and lower MDA content than NTs under drought stress conditions (Cheng et al, 2013). Introduction of the yeast TREHALOSE-6-PHOSPHATASE SYNTHASE1 (TPS1) gene, which functions in the biosynthesis of osmolyte trehalose, into potato leads to drought tolerance by increasing the relative water content in source tissues (leaves) (Kondrák et al, 2012), and by enhancing the accumulation levels of amino acids such as glutamine, glutamate, phenylalanine, proline, and asparagine in sink tissues (tubers), indicating a partial difference in tolerance mechanisms against drought stress in source and sink organs (Juhász et al, 2014).…”

“…Several droughtresponsive genes including AtHB-7, RD28, ALDH22a1, and ERD1-like were induced in transgenic plants under drought conditions, suggesting that StMYB1R-1 functions as a transcription factor involved in the activation of drought-related genes. In a similar study, the Ipomoea batatas (sweet potato) IbMYB1 gene, an R2R3-type MYB transcription factor involved in secondary metabolite production, was overexpressed in potato (Cheng et al, 2013). Transgenic potato plants could tolerate the drought since they accumulated higher levels of secondary metabolites such as phenols, flavonoids, and anthocyanin.…”