Thylakoid membrane oxidoreductase LTO1/AtVKOR is involved in ABA‐mediated response to osmotic stress in Arabidopsis

Abstract

Arabidopsis lumen thiol oxidoreductase 1 (LTO1) - the At4g35760 gene product - was previously found to be related to reactive oxygen species (ROS) accumulation. Here, we show that ROS accumulated in a mutant Arabidopsis line (lto1-2, mutant of LTO1/AtVKOR) under osmotic stress at a higher level than that observed in wild-type and transgenic complemented plants of the lto1-2 mutant (lto1-2C, transgenic complemented plants of lto1-2). Because ROS accumulation in osmotic stress is triggered by abscisic acid (ABA), an ABA-responsive gene, Annexin 1 (AnnAt1), was selected to study the response. Osmotic stress or exogenous ABA can significantly upregulate the transcription of AnnAt1 in wild-type and lto1-2C plants. Only a slight change in the transcriptional abundance of AnnAt1 was observed under osmotic stress in the lto1-2 mutant, but exogenous ABA application could increase the expression of AnnAt1, which suggested that exogenous ABA had a partial complementation role. Because the transcription of AnnAt1 is regulated by ABRE (ABA-responsive elements) binding proteins (AREBs)/ABRE binding factors (ABFs), the expression of AREBs/ABFs was also analyzed. The transcription of AREBs/ABFs in the lto1-2 mutant was not induced by osmotic stress but was significantly upregulated by exogenous ABA, which significantly differs from the wild-type and lto1-2C plant responses. Similarly, the expression of another ABA-responsive gene, RD29B (responsive to desiccation stress gene 29B), in the lto1-2 mutant was also upregulated by exogenous ABA. The partial complementation of mutants by ABA indicated that the ABA signal transduction pathway was not significantly affected in the lto1-2 mutant. Taken together, these results suggest that LTO1 is involved in ABA-mediated response to osmotic stress, possibly by affecting the biosynthesis of endogenous ABA.

Stress-Related Gene Expression Reflects Morphophysiological Responses to Water Deficit

“…S1). The ANN1 gene is a well-established marker of the WD response in Arabidopsis (Konopka-Postupolska et al, 2009;Lu et al, 2015), and its expression was persistently elevated in Col-0 plants grown under conditions similar to those Table II. Partitioning of phenotypic variance among accessions subjected to three watering conditions…”

“…The main selection criterion was the expression level of the drought-response marker ANN1, which was analyzed and quantified during a preliminary experiment (KonopkaPostupolska et al, 2009;Lu et al, 2015). Seedlings of 94 accessions derived from three different collections (McKhann, Weigel, and Nordborg) were screened during that preliminary experiment and provided data on the extremely high and low levels of ANN1 mRNA.…”

Oxidative protein folding: state‐of‐the‐art and current avenues of research in plants

“…It contains a transit peptide at the N‐terminus, which targets the protein to the thylakoid (Feng et al ., ). Loss of LTO1 activity has been associated with a severe depletion of the structural subunits of photosystem II (like D1 protein), which consequently led to a limitation in electron flow from PSII and an increased accumulation of reactive oxygen species and thus severe photoautotrophic growth defect and photoinhibition (Karamoko et al ., ; Lu et al ., , ; Yu et al ., ; Du et al ., ).…”

A homologue of vitamin K epoxide reductase in Solanum lycopersicum is involved in resistance to osmotic stress

“…The results indicated that down‐ and up‐regulation of Sl VKOR in vivo changed the activities of antioxidant enzymes and resulted in differential accumulation of ROS. Our recent study also showed that the involvement of At VKOR to osmotic stress was related to abscisic acid synthesis in Arabidopsis (Lu et al ). In resistance to osmotic stress, Sl VKOR may play an important role in facilitating cross‐talk between ROS homeostasis and the abscisic acid signal pathway.…”

“…Deficiency of AtVKOR results in a photosynthetic defect and the increased accumulation of ROS even under normal growth condition (Lu et al 2013, Yu et al 2014. Recently, it is demonstrated that AtVKOR is involved in an abscisic acid (ABA)-mediated response to osmotic stress in Arabidopsis (Lu et al 2015).…”