Overexpression of the IbOr gene from sweet potato (Ipomea batatas ‘Hoang Long’)in maize increases total carotenoid and β-carotene contents

Abstract

Nutritional quality of most maize varieties is very low due to the lack of lysine and tryptophan and extremely low provitamin A carotenoids including β-carotene, α-carotene, and β-cryptoxanthin. In this study, we report the successful overexpression of the IbOr gene in H145 and H95 inbred maize lines under the control of maize seed-specific promoter globulin 1 (Glo1) for the purpose of improving β-carotene in maize. The results showed that the total carotenoid and β-carotene content of all analyzed transgenic maize plants were significantly higher than those of wild-type lines. For H145-IbOr transgenic maize, in the best line (H145-IbOr.10), the total carotenoid and β-carotene contents were increased up to 10.36-and 15.11-fold, respectively, compared to the wild type (H145-WT). In the case of H95-IbOr transgenic plants, 5.58-fold increase in total carotenoid and 7.63-fold increase in β-carotene were achieved in the H95-IbOr.6 line compared to nontransgenic plants (H95-WT). In all the transgenic plants derived from the wild-type maize line with less carotenoid content (H145-WT), the content of both total carotenoid and β-carotene was higher than in transgenic plants derived from the wild-type maize line having more carotenoid content (H95-WT). Our research is the first in successful overexpression of IbOr gene in maize.

Provitamin a biofortification in maize through genetic engineering and marker-assisted selection

“…The Or gene cloned from yellow-fleshed sweet potato cultivar Hoang Long (named IbOr gene) was transferred into two inbred maize lines (H145 and H95) through A. tumefaciens under the control of maize seed-specific promoter globulin 1 (Glo1). In the best transgenic line (H145-IbOr.10), the total carotenoids and carotene content were increased up to 10.36 (27.6 µg/g DW) and 15.11 (19.35 µg/g DW) fold, comparing to wild-type (2.67 and 1.28 µg/g DW), respectively (Tran et al, 2017). These results indicate the potential use of the Or gene to improve the carotenoid content in maize and other staple crops.…”

“…Hoang Long) and placed under the control of maize seed-specific promoter globulin 1 (Glo1), has been successfully transferred into inbred maize lines and total carotenoid and carotene content of generated transgenic plants were significantly higher than those of wildtype and in the best line, the total carotenoid and -carotene content were increased up to 10.36 and 15.11 fold, respectively (Tran et al, 2017). To our best knowledge, our research is the first to successfully overexpress the IbOr gene in maize.…”

“…The total endosperm carotenoid content in the bestperforming AtOR transgenic maize line was 32-fold higher than wild-type controls (25 µg/g DW) and the other principal carotenoids remained the same. Recently, we have successfully produced transgenic maize plants with considerably increased total carotenoids and -carotene (Tran et al, 2017). The Or gene cloned from yellow-fleshed sweet potato cultivar Hoang Long (named IbOr gene) was transferred into two inbred maize lines (H145 and H95) through A. tumefaciens under the control of maize seed-specific promoter globulin 1 (Glo1).…”

Plant tissue and cell culture in Vietnam: forty-five years of development and the future

“…Shrunken 2 (Sh2) (Tran Thi Luong et al, 2014) and Brittle 2 (Bt2) genes (Nguyen Thi Thu et al, 2014;Nguyen et al, 2016) encoding ADP-glucose pyrophosphorylase-an enzyme that regulates starch synthesis, were successfully transferred into maize and transgenic maize that increase starch content from 10.12 to 16.04% and yield over 5 tons/ha were obtained. As maize is a low-quality food crop (lack of lysine, tryptophan, low provitamin A including α-carotene, β-carotene and β-cryptoxanthin), with the aim of improving the quality of maize, Tran et al (2017) had transferred the IbOr gene from the Hoang Long sweet potato variety into several maize lines and created transgenic maize plants with increased -carotene content more than 10 fold, contributing to improving the nutritional quality of maize (Tran et al, 2017;Tran Thi Luong & Nguyen Duc Thanh, 2018…”

“…Many works implemented in Vietnam have been published in prestigious international journals and monographs. These are studies on factors affecting plant cell tissue culture (Duong Tan Nhut, 2005;Duong Tan Nhut et al, 2005;2006a;2007a, 2007b2008a, 2015b2017b;Nguyen Hong Vu et al, 2006;Nguyen Ba Nam et al, 2016;Vu et al, 2019), on in vitro propagation (Duong Tan Nhut, 1998Nhut, , 2003Duong Tan Nhut et al, 2004a, 2009c, on acquisition of secondary substances from plant tissues and cells (Nguyen Hoang Loc & Nguyen Thi Tam An, 2010;Nguyen Hoang Loc & Nguyen Thi Duy Nhat, 2013;Nguyen Hoang Loc et al, 2014, 2017Nguyen Huu Thuan Anh et al, 2016;Nguyen Thanh Giang et al, 2016;Nguyen Huu Nhan & Nguyen Hoang Loc, 2017Nguyen Thi Nhat Linh et al, 2019), on TCL culture technique (Duong Tan Nhut et al, 2007e, 2012aNhut et al, 2007e, , 2012bNhut et al, 2007e, , 2012cNhut et al, 2007e, , 2013, on gene transfer in plants (Nguyen et al, 2016;Tran et al, 2017;Vi et al, 2017) and on photoautotrophic culture (Nguyen et al, 1999(Nguyen et al, , 2001Nguyen & Kozai, 2005;Nguyen et al, 2016Nguyen et al, , 2020. Although these contributions are still modest, it has made a remarkable impression in the world of plant tissue and cell culture.…”