Gene knockout of glutathione reductase 3 results in increased sensitivity to salt stress in rice

Abstract

Glutathione reductase (GR) is one of important antioxidant enzymes in plants. This enzyme catalyzes the reduction of glutathione disulfide (GSSG) to reduced glutathione (GSH) with the accompanying oxidation of NADPH. Previously, we showed that salt-stress-responsive GR3 is a functional protein localized in chloroplasts and mitochondria in rice. To learn more about the role of GR3 in salt-stress tolerance, we investigated the response to 100 mM NaCl treatment in wild-type rice (WT); GR3 knockout mutant of rice (gr3); and the functional gr3-complementation line (C1). Rice GR3 was primarily expressed in roots at the seedling stage and ubiquitously expressed in all tissues except the sheath at heading stage. GR3 promoter-GUS was expressed in the vascular cylinder and cortex of root tissues in rice seedlings, vascular tissue of nodes, embryo and aleurone layer of seeds, and young flowers. Under both normal and salt-stress conditions, total GR activity was decreased by 20 % in gr3. Oxidative stress, indicated by malondialdehyde content, was greater in gr3 than the WT under salt stress. As compared with the WT, gr3 was sensitive to salt and methyl viologen; it showed inhibited growth, decreased maximal efficiency of photosystem II, decreased GSH and GSSG contents, and the ratio of GSH to GSSG. Conversely, the gr3-complementation line C1 rescued the tolerance to methyl viologen and salinity and recovered the growth and physiological damage caused by salinity. These results reveal that GR3 plays an important role in salt stress tolerance by regulating the GSH redox state in rice.

Evidence of a significant role of glutathione reductase in the sulfur assimilation pathway

“…Therefore, these results suggest a link between the higher levels of these genes to the synthesis of cysteine and glutathione under stress, as we propose here. Moreover, the current results also suggest an explanation for the high sensitivity to oxidative stress of transgenic rice and tobacco plants having lower levels of GR (Aono et al , ; Ding et al , , ; Wu et al , ). This sensitivity might be the consequence of a lesser conversion of GSSG to GSH, but the results of the current study suggest an additional explanation: the sensitivity could result from the lower production of cysteine and glutathione in these plants during the stress due to lower GR activity that affects APR activity.…”

“…To further reveal the roles of GR under stress conditions, the researchers reduced or increased the expression level of the GR genes and studied the effects. As expected, transgenic tobacco ( Nicotiana tabacum ) and rice plants with decreased GR activity exhibited enhanced sensitivity to oxidative stress (Aono et al , ; Ding et al , , ; Wu et al , ), while plants overexpressing the bacterial Escherichia coli gene in chloroplasts or cytosol in tobacco and poplar plants showed greater tolerance to oxidative stress than the control WT plants (Foyer et al , , ; Aono et al , ; Noctor et al , ; Lederer and Boger, ; Poage et al , ). However, plants overexpressing GR that originated from plants gave ambiguous results under stress.…”

JcDREB2, a Physic Nut AP2/ERF Gene, Alters Plant Growth and Salinity Stress Responses in Transgenic Rice

“…The products of the OsHKT1;1 gene are crucial for salt tolerance in rice through the exclusion of Na + ions from sensitive cells (Ren et al, 2005). The OsGR3 gene products are involved in scavenging reactive oxygen species (Wu et al, 2015). Increases in the levels of expression of OsHKT1;1 , OsP5CS and OsGR3 under salt treatment were strongly impaired in the leaves of two OeJcDREB2 plants ( Figure 7H ).…”

“…Our results indicated that the expression of stress-responsive genes such as OsHKT1;1 , OsP5CS , OsGR3 , and SNAC1 was significantly lower in transgenic rice compared to wild-type under salinity stress ( Figure 7H ). Related research has shown that overexpressing these genes may improve the tolerance of transgenic plants to salinity stress (Ren et al, 2005; Hu et al, 2006; Wu et al, 2015). Our findings indicate that JcDREB2 affected salt stress tolerance in the transgenic rice plants at least partially owing to decreases in the expression of stress-responsive genes under salinity stress.…”

Salinity Response in Chloroplasts: Insights from Gene Characterization

“…Tobacco plants overexpressing genes of MDHAR [23] and DHAR [24] showed significantly high enzyme activities of MDHAR and DHAR, as well as an increased level of reduced AsA and improved survival under salt stress. In addition, OsGR3 was markedly induced in rice under salt treatment [25], and the salinity sensitivity of rice was increased when the OsGR3 gene was knocked out [26]. These results indicate that stromal ROS scavenging in chloroplasts is crucial for redox homeostasis and supplying NADP + , leading to the reduced loading of the ETC.…”