MdGGT1 Impacts Apple miR156 Precursor Levels via Ontogenetic Changes in Subcellular Glutathione Homeostasis

Abstract

The vegetative phase change in flowering plants is controlled by microRNA156 (miR156) under transcriptional regulation. However, the developmental signals upstream of miR156 are not well understood. The glutathione/glutathione disulfide (GSH/GSSG) ratios and GSH levels decline significantly during phase change, which is consistent with miR156 expression in apple ( Malus domestica Borkh.). Here, we found that the content of protein conjugated glutathione was remarkably higher in chloroplasts and nuclei of adult than juvenile phase apple hybrids. The decrease in miR156 expression was most relevant to the activities of serine acetyltransferase (SAT) and soluble γ-glutamyl transpeptidase (GGT), and the expressions of MdGGT1 or MdSATs . Transgenic apples over-expressing MdMIR156 or miR156-mimetic (MIM156) did not alter MdGGT1 expression or the soluble GGT activity. Inhibition of GGT activity with serine-borate complex or acivicin led to significant reduction in GSH content, the GSH/GSSG ratio, and the expressions of MdMIR156a5 , MdMIR156a12 , and miR156. Depletion of GSH with diethyl maleate without altering GGT activity caused a dramatic decrease in the expression of MdMIR156a5 , MdMIR156a12 , and miR156. Manipulating GGT activity and GSH homeostasis by transgenic over-expressing or RNAi MdGGT1 increased or decreased MdMIR156a5 and MdMIR156a12 levels, respectively. These data provided novel evidence that MdGGT1 participates in transcriptional level of transcription regulation of miR156 precursors during ontogenesis. HIGHLIGHTS - MdGGT1 affects thiol redox status and indirectly participates in the regulation of miR156 expression during vegetative phase change.

MicroRNA156 (miR156) Negatively Impacts Mg-Protoporphyrin IX (Mg-Proto IX) Biosynthesis and Its Plastid-Nucleus Retrograde Signaling in Apple

“…This indicated that the NTRC/2-Cys Prx level was robustly maintained during the phase change (Figure 3). In this study, both GSH content and the GSH/GSSG ratio decreased significantly during ontogenesis, which supported our previous hypothesis that a shift in major antioxidants from GSH to ASC during the phase change attenuated the cellular ROS scavenging ability [11,18,22]. This was consistent with that GSH plays a key role in ASC-GSH coupled non-enzyme ROS scavenging in plant cells [59].…”

“…We examined whether tetrapyrrole-PNRS was affected by the GSH status by using GL-3 transgenic lines over-expressing gamma-glutamyl transferase gene1 (OEMdGGT1) and MdGGT1-RNAi lines. It is reported that GSH levels and miR156 expression are elevated in OEMdGGT1 and decreased in MdGGT1-RNAi lines [22]. We found that Mg-Proto IX and heme levels were relatively lower in OEMdGGT1 lines but were significantly higher in MdGGT1-RNAi lines compared with WT (Figure 9A,B).…”

“…Moreover, both the content of ascorbate (ASC), an important ROS scavenger, and the ascorbate/dehydroascorbate ratio increase during the phase change in apple [18]. In contrast, the concentration of glutathione (GSH), another major ROS scavenger in the plastid, and glutathione/glutathione disulfide (GSH/GSSG) ratio are significantly lower in adult phase than in juvenile phase [22]. Plastid H 2 O 2 also perceives stress and developmental cues and triggers PNRS, which regulates nuclear gene transcription [23].…”

Temporal Control of Seed Development in Dicots: Molecular Bases, Ecological Impact and Possible Evolutionary Ramifications

“…The importance of ROS scavenging is underpinned by the similar phenotype of Arabidopsis pex10 mutants impaired in peroxisome biogenesis [154] and a more permissive delayed embryogenesis phenotype in str1 str2 mutants impaired in RBOH-associated mitochondrial proteins [155]. Provided that ROS can serve as signaling molecules [156,157], it is possible that ROS formation, scavenging, and signal transduction may represent the prominent players in novel embryonic timing control mechanisms as well.…”

A fluorine-18 labeled radiotracer for PET imaging of γ-glutamyltranspeptidase in living subjects

“…11 Moreover, abnormally high expression level of GGT could lead to the breakdown of redox homeostasis in intracellular environment and eventually result in cancerization. 5,12 GGT can promotes the growth and proliferation of tumor cells by mediating the circulation of g-Glu in tumor cells. 13 It also can promotes cancer metastasis and drug resistance of tumors.…”