bims-plasge Biomed news
on Plastid genes
Issue of 2018‒10‒14
two papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Biochem Biophys Res Commun. 2018 Oct 03. pii: S0006-291X(18)32077-1. [Epub ahead of print]
    Wang J, Xia H, Zhao SZ, Hou L, Zhao CZ, Ma CL, Wang XJ, Li PC.
      In Arabidopsis thaliana (Arabidopsis), Acetyl-CoA Carboxylase 2 (ACC2) is a nuclear DNA-encoded and plastid-targeted enzyme that catalyzes the conversion of acetyl-CoA to malonyl-CoA. ACC2 improves plant growth and development when chloroplast translation is impaired. However, little is known about the upstream signals that regulate ACC2. Here, through analyzing the transcriptome changes in brz-insensitive-pale green (bpg) 2-2, a pale-green mutant with impaired chloroplast gene expression resulting from loss of the BPG2 function, we found that the level of ACC2 was significantly up-regulated. Through performing genetic analysis, we further demonstrated that loss of the GENOMES UNCOUPLED 1 (GUN1) or GUN5 function partly perturbed the up-regulation of ACC2 in the bpg2-2 mutant, whereas ABA INSENSITIVE 4 (ABI4)-function-loss had no clear effect on the ACC2 expression. Furthermore, when plants were treated with plastid translation inhibitors, such as lincomycin and spectinomycin, the ACC2 transcriptional level was also markedly increased in a GUN-dependent manner. In conclusion, our results suggested that the GUN-involved plastid-to-nucleus retrograde communication played a role in regulating ACC2 in Arabidopsis.
    Keywords:  ACC2; BPG2; GUN1; GUN5; Plastid; Retrograde signaling
  2. Mol Plant. 2018 Oct 04. pii: S1674-2052(18)30301-0. [Epub ahead of print]
    Jiang Y, Xie Q, Wang W, Yang J, Zhang X, Yu N, Zhou Y, Wang E.
      Most land plants evolve a mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi to improve nutrient acquisition from the soil. In return, up to 20% of host plant photosynthate is transferred to the mycorrhizal fungus in the form of lipids and sugar. Nutrient exchange must be regulated by both partners in order to maintain a reliable symbiotic relationship. However, the mechanisms underlying the regulation of lipid transfer from plant to AM fungus remain elusive. Here, we show that Medicago truncatula AP2/EREBP transcription factor WRI5a, and likely its two homologs WRI5b/Erf1 and WRI5c, are master regulators of AM symbiosis by controlling lipid transfer and periarbuscular membrane formation. We found that WRI5a binds the AW-box cis-regulatory elements in the promoters of STR and MtPT4 in M. truncatula, which encodes a periarbuscular membrane-localized ABC transporter required for lipid transfer from the plant to AM fungi-and a phosphate transporter required for phosphate transfer from AM fungi to the plant, respectively. The M. truncatula wri5a mutant and RNAi composite plants hairy roots displayed impaired arbuscule formation, whereas overexpression of WRI5a resulted in enhanced expression of STR and MtPT4, suggesting that WRI5a regulates bidirectional symbiotic nutrient exchange. Moreover, we found that WRI5a and RAM1 (Required for Arbuscular Mycorrhization symbiosis 1) encoding a GRAS-domain transcription factor regulate each other at the transcriptional level, forming a positive feedback loop for regulating AM symbiosis. Our data suggest a role for WRI5a in controlling lipid transfer and periarbuscular membrane formation via the regulation of genes for the biosynthesis and supply of fatty acids and phosphate uptake in arbuscule-containing cells.
    Keywords:  AW-box; Mycorrhizal symbiosis; lipid transfer; transcription factor