Molecular cloning and characterization of CrNCED1, a gene encoding 9-cis-epoxycarotenoid dioxygenase in Citrus reshni, with functions in tolerance to multiple abiotic stresses

Abstract

Abscisic acid (ABA) is an important stress phytohormone that plays an essential role in mediating the signaling networks associated with plant responses to various abiotic stresses. In the present study, we isolated a gene CrNCED1 encoding the rate-limiting enzyme of ABA synthesis, 9-cis-epoxycarotenoid dioxygenase (NCED), from Citrus reshni. Expression patterns of CrNCED1 varied among different tissues, in which higher levels were measured in the leaves than in the roots. The steady-state mRNA levels of CrNCED1 were progressively elevated by dehydration and ABA, only transiently induced by cold, but not affected by salt. To examine its function in stress tolerance, transgenic tobacco (Nicotiana nudicaulis) plants constitutively overexpressing CrNCED1 were generated, which contained higher ABA levels than the wild type (WT) under both normal growth conditions and drought stress. The transgenic lines displayed enhanced tolerance to dehydration, drought, salt and oxidative stresses when compared with the WT. Lower levels of reactive oxygen species (H₂O₂ and O₂⁻) were detected in the transgenic plants than in the WT under dehydration and salt stress. On the contrary, transcript levels of several genes associated with ROS scavenging, osmoticum adjustment, and water maintenance, and activities of two antioxidant enzymes were higher in the transgenic plants relative to the WT under the dehydration stress. Taken together, CrNCED1 overexpression confers enhanced tolerance to multiple abiotic stresses, which may be, at least in part, ascribed to the positive activation of the stress-responsive genes.

Heterologous expression of EsABA1 enhances salt tolerance with increased accumulation of endogenous ABA in transgenic tobacco

“…In Arabidopsis, the expression of AtZEP was induced by drought, salt, and polyethylene glycol (Xiong et al, 2002). Similar results have been observed in other ABA biosynthetic genes, such as NCEDs (Qin and Zeevaart, 1999;Xian et al, 2014). Moreover, a series of recent findings have shown that overexpression of the ABA biosynthetic genes in transgenic plants enhances abiotic stress tolerance under increased ABA levels.…”

“…To cope with the deleterious effects of ROS, ROS in plant cells can be modulated via important antioxidants such as the enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) (Noctor and Foyer, 1998;Asada, 1999;Kausar et al, 2013;Gharari et al, 2014). Some recent reports have indicated that elevated ABA biosynthesis can significantly enhance the activities of antioxidant enzymes and increase the accumulation of osmolytes such as proline and malondialdehyde (MDA), which help plants tolerate stress by maintaining osmotic balance within the cells (Yue et al, 2012;Xian et al, 2014). To date, much effort has been made to understand the regulatory mechanism of ABA biosynthesis.…”

“…The transgenic cottons ectopically expressing At-LOS5 exhibited more tolerance to drought stress than control plants (Yue et al, 2012). In addition, the overexpression of NCED homologs encoding the rate-limiting enzymes of ABA biosynthesis has been shown to improve the tolerance of transgenic plants to multiple abiotic stresses by increasing ABA levels (Qin and Zeevaart, 2002;Xian et al, 2014). Thus, identification of genes involved in pathways of ABA biosynthesis can be useful for improving the tolerance of transgenic plants to various abiotic stresses.…”

A R2R3 MYB transcription factor from ash positively regulates salt response in tobacco

“…In addition, multiple genes that have been reported to be involved in the process of ABA signal transduction were also up-or downregulated. For example, overexpression of NCED and AREB could improve drought and salt stress tolerance in transgenic plants (Xian et al, 2014;Yoshida et al, 2015). The overexpression of FvMYB2 increases the transcripts of the ABA synthesis gene NtNCED and ABA signaling transduction gene NtAREB in tobacco under salt stress, indicating that FvMYB2 may be a positive regulator of ABA signaling and confers salt stress tolerance at least partially by ABA signal pathway.…”

Effect of overexpression of citrus 9-cis-epoxycarotenoid dioxygenase 3 (CsNCED3) on the physiological response to drought stress in transgenic tobacco

“…The overexpression of citrus NCED5 was also shown to be correlated with the ABA levels in ripening fruits (Agustí et al, 2007). A citrus NCED3 ortholog, CrNCED1, was isolated from 'Cleopatra' mandarin (Citrus reshni) and overexpressed in transgenic tobacco plants, which exhibited 1.3-3.0-fold higher levels of ABA under normal growth conditions and enhanced the ABA synthesis and tolerance under dehydration, drought, salt, and oxidative stresses when compared with WT (Xian et al, 2014). However, the effects of CrNCED1 expression on physiological parameters of transgenic plants were not evaluated in the afore-mentioned study.…”