A lycopene β-cyclase gene, IbLCYB2, enhances carotenoid contents and abiotic stress tolerance in transgenic sweetpotato

Abstract

Lycopene β-cyclase (LCYB) is an essential enzyme that catalyzes the conversion of lycopene into α-carotene and β-carotene in carotenoid biosynthesis pathway. However, the roles and underlying mechanisms of the LCYB gene in plant responses to abiotic stresses are rarely known. This gene has not been used to improve carotenoid contents of sweetpotato, Ipomoea batatas (L.) Lam.. In the present study, a new allele of the LCYB gene, named IbLCYB2, was isolated from the storage roots of sweetpotato line HVB-3. Its overexpression significantly increased the contents of α-carotene, β-carotene, lutein, β-cryptoxanthin and zeaxanthin and enhanced the tolerance to salt, drought and oxidative stresses in the transgenic sweetpotato (cv. Shangshu 19) plants. The genes involved in carotenoid and abscisic acid (ABA) biosynthesis pathways and abiotic stress responses were up-regulated in the transgenic plants. The ABA and proline contents and superoxide dismutase (SOD) activity were significantly increased, whereas malonaldehyde (MDA) and HO contents were significantly decreased in the transgenic plants under abiotic stresses. The overall results indicate that the IbLCYB2 gene enhances carotenoid contents and abiotic stress tolerance through positive regulation of carotenoid and ABA biosynthesis pathways in sweetpotato. This gene has the potential to improve carotenoid contents and abiotic stress tolerance in sweetpotato and other plants.

A Sweetpotato Auxin Response Factor Gene (IbARF5) Is Involved in Carotenoid Biosynthesis and Salt and Drought Tolerance in Transgenic Arabidopsis

“…Total RNA was extracted from freshly harvested storage roots of HVB-3 and transcribed into first-strand cDNA according to the method of Kang et al (2018) . The full-length cDNA of IbARF5 was amplified with specific primers ( Supplementary Table S1 ) by rapid amplification of cDNA ends (RACE) method.…”

“…In nature, more than 750 kinds of carotenoids are characterized structurally, which are widely found in bacteria, fungi, algae, and plants ( Hirschberg , 2001 ; Takaichi, 2011 ). The biosynthesis pathway of carotenoids has been extensively studied in plants, and nearly all of the key genes have been isolated and characterized ( Cunningham and Gantt, 1998 ; Fraser and Bramley, 2004 ; Colasuonno et al, 2017 ; Kang et al, 2018 ). Abiotic stresses, especially salt and drought, seriously affect the productivity and cultivation expansion of crop plants worldwide, accordingly, to develop their high tolerance to salt and drought is highly desirable ( Zhu, 2002 ; Lindemose et al, 2013 ; Zhai et al, 2016 ; Li et al, 2017 ).…”

“… Kang et al (2017) summarized the improvement of carotenoids by gene engineering in sweetpotato. Overexpression of the genes related to carotenoid biosynthesis have been shown to increase the contents of carotenoids and enhance the tolerance to abiotic stresses in sweetpotato ( Kim et al, 2012 , Kim et al, 2013b ; Yu et al, 2013 ; Kim et al, 2014 ; Li et al, 2017 ; Kang et al, 2018 ). To date, ARFs have not been reported in sweetpotato.…”

Identifying a Carotenoid Cleavage Dioxygenase (CCD4) Gene Controlling Yellow/White Fruit Flesh Color of “Piqiutao” (White Fruit Flesh) and Its Mutant (Yellow Fruit Flesh)

“…The relative expression of LYCB and LYCE determines the carotenoid flux, which affects the α-/β-carotene ratio (Fu et al 2019). The βcarotene content has been greatly improved after silencing LYCE by RNAi, and the overexpression of LYCB2 upregulated carotenoid-related genes and increased βcarotene content in sweet potato (Kim et al 2013;Kang et al 2018). Finally, carotenoid cleavage oxygenases (CCOs) catalyze the degradation process of carotenoids, in which carotenoids are cleaved into various apocarotenoids by specifically cutting the conjugated double bond of C 40 carotenoids.…”

Status of research on the sweetpotato biotechnology and prospects of the molecular breeding on marginal lands

“…한 사료로서의 곡물 사용이 증가하고 있다 (Cargill 2014 Carotenoid accumulation and enhanced tolerance to abiotic stress Kang et al (2018) Promoter Sporamin High expression in storage roots Hattori et al (1991 (Ye et al 2000;Paine et al 2005), "Golden potato" (Diretto et al 2007a,b) 등 이 개발되었다. 하지만 생합성 유전자의 과발현을 통한 카 로티노이드 과다 생합성은 ABA의 과다생성이나 GA의 생 합성을 방해하여 발아가 지연되거나 성장이 잘 되지 않는 부 작용도 가지고 있다 (Shewmaker et al 1999;Lindgren et al 2003…”