pTAC10, a Key Subunit of Plastid-Encoded RNA Polymerase, Promotes Chloroplast Development

Abstract

Regulation of photosynthetic gene expression by plastid-encoded RNA polymerase (PEP) is essential for chloroplast development. The activity of PEP largely relies on at least 12 PEP-associated proteins (PAPs) encoded in the nuclear genome of plant cells. A recent model proposed that these PAPs regulate the establishment of the PEP complex through broad PAP-PEP or PAP-PAP interactions. In this study, we identified the Arabidopsis () seedling-lethal mutant , which has defects in chloroplast development, and found that the mutant phenotype is caused by the suppression of (). Analysis of the heterozygous mutant and -overexpressing transgenic plants indicated that the expression level of is tightly linked to chloroplast development. Characterization of the interaction of pTAC10 with PAPs revealed that pTAC10 interacts with other PAPs, such as FSD2, FSD3, TrxZ, pTAC7, and pTAC14, but it does not interact with PEP core enzymes, such as rpoA and rpoB. Analysis of pTAC10 interactions using truncated pTAC10 proteins showed that the pTAC10 carboxyl-terminal region downstream of the S1 domain is involved in the pTAC10-PAP interaction. Furthermore, overexpression of truncated lacking the C-terminal regions downstream of the S1 domain could not rescue the mutant phenotype and induced an abnormal whitening phenotype in Columbia-0 plants. Our observations suggested that these pTAC10-PAP interactions are essential for the formation of the PEP complex and chloroplast development.

Quantitative proteome profile of water deficit stress responses in eastern cottonwood (Populus deltoides) leaves

“…Moreover, the cyclic drought experiment provides a valuable perspective on proteome changes influenced by drought effects of previous cycles; changes likely reflect a strategy to cope with a fluctuation in water status. Most associated proteins correlating with stomatal regulation function in phytochrome-mediated photomorphogenesis [ 48 ] (e.g., Potri.016G018300, FHY3 ; up-regulated ~31 fold) and circadian signaling [ 49 ] (e.g., Potri.004G168400, XCT ; up-regulated ~11 fold) that impact developmental and physiological processes, including chloroplast osmolarity [ 50 ] (e.g., Potri.002G105900, MSL2 ; up-regulated ~29 fold) and chloroplast development [ 51 ] (e.g., Potri.015G091700, TAC10 ; up-regulated ~16 fold). In addition, we identified a protein (Potri.011G112400, STO1 ; up-regulated ~15 fold) that is localized to the chloroplast stroma and thylakoid membrane, and recently implicated in stress responses that correlated with changes in morpho-physiological traits [ 52 ].…”

FRUCTOKINASE‐LIKE PROTEIN 1 interacts with TRXz to regulate chloroplast development in rice

“…pTAC8/PHOTOSYSTEM I P SUBUNIT (PSI‐P) is a subunit of plant photosystem I that is involved in grana formation (Hansson and Vener ; Armbruster et al ). pTAC10 interacts with other TACs, such as FSD2, FSD3, TRXz, pTAC7, and pTAC14, all of which are essential for PEP‐related chloroplast biogenesis (Chang et al ). pTAC12/HEMERA (HMR) functions in the nucleus, where it acts specifically in phytochrome‐dependent light signaling, and the hmr mutant phenotype is albino, etiolated under continuous red and far‐red light, and is seedling lethal (Chen et al ).…”

White Leaf and Panicle 2, encoding a PEP-associated protein, is required for chloroplast biogenesis under heat stress in rice

“…PAP6 and FLN2) during chloroplast biogenesis ( Arsova et al , 2010 ; Wimmelbacher and Börnke, 2014 ). Moreover, proteins such as PAP3 (pTAC10), PAP5 (pTAC12), PAP8 (pTAC6), and PAP12 (pTAC7) with unknown functions have been suggested to be involved in PEP-mediated plastid gene expression and to promote chloroplast development ( Chang et al ., 2017 ; Kindgren and Strand, 2015 ; Pfalz et al , 2006 ). Although there has been rapid progress in the understanding of the PEP complex in Arabidopsis, studies concerning the transcription process in chloroplasts, and especially the functions of PEP the complex, are notably limited in important crops such as rice.…”