Homologous expression of cytosolic dehydroascorbate reductase increases grain yield and biomass under paddy field conditions in transgenic rice (Oryza sativa L. japonica)

Abstract

Dehydroascorbate reductase (DHAR, EC 1.8.5.1) maintains redox pools of ascorbate (AsA) by recycling oxidized AsA to reduced AsA. To investigate whether DHAR affects rice yield under normal environmental conditions, cDNA-encoding DHAR (OsDHAR1) was isolated from rice and used to develop OsDHAR1-overexpressing transgenic rice plants, under the regulation of a maize ubiquitin promoter. Incorporation and expression of the transgene in transgenic rice plants was confirmed by genomic polymerase chain reaction (PCR), semi-quantitative reverse transcription PCR (RT-PCR), western blot, and enzyme activity. The expression levels were at least twofold higher in transgenic (TG) rice plants than in control wild-type (WT) rice plants. In addition, OsDHAR1-overexpression in seven-independent homologous transgenic plants, as compared to WT plants, increased photosynthetic capacity and antioxidant enzyme activities under paddy field conditions, which led to an improved AsA pool and redox homeostasis. Furthermore, OsDHAR1 overexpression significantly improved grain yield and biomass due to the increase of culm and root weights and to enhance panicle and spikelet numbers in the same seven independent TG rice plants during the farming season (2010 and 2011) in South Korea. The OsDHAR protein contained the redox-active site (Cys20), as well as the conserved GSH-binding region, GSH-binding motif, glutathione-S-transferase (GST) N-terminal domain, C-terminal domain interface, and GST C-terminal domain. Therefore, our results indicate that OsDHAR1 overexpression, capable of functioning in AsA recycling, and protein folding increases environmental adaptation to paddy field conditions by the improving AsA pool and redox homeostasis, which enhances rice grain yield and biomass.

Transcriptional profile of genes involved in ascorbate glutathione cycle in senescing leaves for an early senescence leaf (esl) rice mutant

“…According to previous studies, the expression of OsDHARs in rice leaves could effectively assist the other antioxidant enzymes that are involved in the AsA-GSH cycle in reducing the effects of oxidative stress (Noctor and Foyer, 1998). The upregulated DHAR transcripts were detected for some plants and tissues exposed to short-term abiotic stresses (Kim et al, 2013). In this study, two OsDHARs (OsDHAR1 and OsDHAR2) showed genotypic changes in their transcript levels and temporal patterns, in that, the two OsDHARs showed consistently repressed expressions for the esl rice leaves during the whole sampling period (Fig.…”

“…For OsMDHAR, this small gene family comprises five isoform members: two cytosolic isoforms (OsMDHAR1 and Os MDHAR2), two membrane-bound peroxisomal isoforms (OsMDHAR3 and OsMDHAR4), and one chloroplastic isoform (OsMD-HAR5) (Teixeira et al, 2005). DHAR enzymes are encoded by two isoform genes (OsDHAR1, and OsDHAR2) (Kim et al, 2013). However, to date, information on the transcriptional profile and temporal patterns of these isoform expressions during rice leaf senescence is lacking, and the interaction between the transcript expression of distinct OsAPX isoform genes and H 2 O 2 accumulation in the initiation and progression of the senescing leaves remains unclear.…”

WITHDRAWN: Physiological and biochemical characterization of tomato transgenic lines overexpressing Arabidopsis thaliana cold responsive-element binding factor 3 (AtCBF3) gene under chilling stress

“…During this study, we examined the effect of AtCBF3 gene with respect to ascorbic acid contents; which is an antioxidant enzyme and creates chilling tolerance in tomato transgenic lines (Kim et al, 2013). Under normal temperature (25 ºC), AtCBF3 plants and WT plants did not exhibit any distinguishable differences in AsA contents.…”

“…Plants hold antioxidant enzymes that have been best characterized for their protective roles in photosynthetic machinery by scavenging toxic free radicals and also act as signaling molecules to regulate the expression of cold defense genes (Gill et al, 2013). Ascorbic acid (AsA) is an essential antioxidant that detoxifies ROS generated during cold stress, and it also acts as a co-factor for many enzymes (Kim et al, 2013). AsA has been reported to regulate cell division and growth by acting as a signal transduction molecule (Green and Fry, 2005).…”

Ascorbate biosynthesis and its involvement in stress tolerance and plant development in rice (Oryza sativa L.)

“…However, detailed information about AsA biosynthesis in rice is missing. The homologous overexpression of the recycling enzyme dehydroascorbate reductase (DHAR) in rice lead to enhanced foliar AsA redox state and improved grain yield and biomass under field conditions (Kim et al 2013). Together, these investigations suggest that the understanding of AsA biosynthesis in rice has important implications in the breeding for biomass and stress related traits of the world's most important food crop.…”