The ANGULATA7 gene encodes a DnaJ‐like zinc finger‐domain protein involved in chloroplast function and leaf development in Arabidopsis

Abstract

The characterization of mutants with altered leaf shape and pigmentation has previously allowed the identification of nuclear genes that encode plastid-localized proteins that perform essential functions in leaf growth and development. A large-scale screen previously allowed us to isolate ethyl methanesulfonate-induced mutants with small rosettes and pale green leaves with prominent marginal teeth, which were assigned to a phenotypic class that we dubbed Angulata. The molecular characterization of the 12 genes assigned to this phenotypic class should help us to advance our understanding of the still poorly understood relationship between chloroplast biogenesis and leaf morphogenesis. In this article, we report the phenotypic and molecular characterization of the angulata7-1 (anu7-1) mutant of Arabidopsis thaliana, which we found to be a hypomorphic allele of the EMB2737 gene, which was previously known only for its embryonic-lethal mutations. ANU7 encodes a plant-specific protein that contains a domain similar to the central cysteine-rich domain of DnaJ proteins. The observed genetic interaction of anu7-1 with a loss-of-function allele of GENOMES UNCOUPLED1 suggests that the anu7-1 mutation triggers a retrograde signal that leads to changes in the expression of many genes that normally function in the chloroplasts. Many such genes are expressed at higher levels in anu7-1 rosettes, with a significant overrepresentation of those required for the expression of plastid genome genes. Like in other mutants with altered expression of plastid-encoded genes, we found that anu7-1 exhibits defects in the arrangement of thylakoidal membranes, which appear locally unappressed.

Functional analysis of mTERF5 and mTERF9 contribution to salt tolerance, plastid gene expression and retrograde signalling in Arabidopsis thaliana

“…Consistent with this, the angulata7‐1 mutant, affected in a plastid nucleoid protein of unknown function, also exhibited aberrant leaf development and synergistically interacted with gun1‐1 (Muñoz‐Nortes et al . ). Like mterf9, also coe1 (affected in mTERF4 ) synergistically interacted with gun1 (Sun et al .…”

Novel DNAJ‐related proteins in Arabidopsis thaliana

“…DNAJE1.6/LQY1 plays a role in the maintenance of photosystem II (Lu et al ., ), and DNAJE1.7/PSA2 is required for photosystem I accumulation (Fristedt et al ., ). DNAJE1.11/ANGULATA7 is involved in chloroplast development and leaf development (Munoz‐Nortes et al ., ). Recently, DNAJE1.14/HCF222 was found to be essential for seedling establishment and photosynthesis (Hartings et al ., ).…”

“…Several A. thaliana proteins such as BSD2 (Brutnell et al ., ), ORANGE (Lu et al ., ), PSA2 (Fristedt et al ., ), SCO2 (Tanz et al ., ), PTAC5 (Zhong et al ., ), and ANGULATA7 (Munoz‐Nortes et al ., ) have been recently coined as ‘DnaJ cysteine‐rich domain protein’, ‘DnaJ‐type zinc finger domain proteins’ or ‘DNAJ‐like proteins’. In fact, these proteins lack the J‐domain and C‐terminal domain and contain only a zinc‐finger domain similar to the one of DNAJA proteins.…”

Plastid ribosomal protein LPE2 is involved in photosynthesis and the response to C/N balance in Arabidopsis thaliana

“…PGE-triggered retrograde signaling leads to embryo lethal phenotypes (Garcia et al 2008;Hsu et al 2010;Babiychuk et al 2011). Retrograde signals have important functions in leaf lamina and mesophyll cells' development; this is supported by altered leaf shape and pigmentation in plants lacking ANU7 (Munoz-Nortes et al 2017). Additionally, retrograde signaling plays an important role in cell expansion and photosynthesis activation via tetrapyrroles (Andriankaja et al 2012).…”