The collaborative non‐self‐recognition model for S‐
The mitochondrial and chloroplast
- NSF-PAR ID:
- Publisher / Repository:
- Date Published:
- Journal Name:
- The Plant Journal
- Page Range / eLocation ID:
- p. 1116-1126
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The collaborative non‐self‐recognition model for S‐
RNase‐based self‐incompatibility predicts that multiple S‐locus F‐box proteins ( SLFs) produced by pollen of a given S‐haplotype collectively mediate ubiquitination and degradation of all non‐self S‐ RNases, but not self S‐ RNases, in the pollen tube, thereby resulting in cross‐compatible pollination but self‐incompatible pollination. We had previously used pollen extracts containing GFP‐fused S2‐ SLF1 ( SLF1 with an S2‐haplotype) of Petunia inflatafor co‐immunoprecipitation (Co‐ IP) and mass spectrometry ( MS), and identified Pi CUL1‐P (a pollen‐specific Cullin1), Pi SSK1 (a pollen‐specific Skp1‐like protein) and Pi RBX1 (a conventional Rbx1) as components of the SCFS2– SLF1complex. Using pollen extracts containing Pi SSK1: FLAG: GFPfor Co‐ IP/ MS, we identified two additional SLFs ( SLF4 and SLF13) that were assembled into SCFSLFcomplexes. As 17 genes ( SLF to SLF1 ) have been identified in SLF17 S2and S3pollen, here we examined whether all 17 SLFs are assembled into similar complexes and, if so, whether these complexes are unique to SLFs. We modified the previous Co‐ IP/ MSprocedure, including the addition of style extracts from four different S‐genotypes to pollen extracts containing Pi SSK1: FLAG: GFP, to perform four separate experiments. The results taken together show that all 17 SLFs and an SLF‐like protein, SLFLike1 (encoded by an S‐locus‐linked gene), co‐immunoprecipitated with Pi SSK1: FLAG: GFP. Moreover, of the 179 other F‐box proteins predicted by S2and S3pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co‐immunoprecipitated with Pi SSK1: FLAG: GFP. These results suggest that SCFSLFcomplexes have evolved specifically to function in self‐incompatibility.
Summary Eukaryotic cells represent an intricate collaboration between multiple genomes, even down to the level of multi‐subunit complexes in mitochondria and plastids. One such complex in plants is the caseinolytic protease (Clp), which plays an essential role in plastid protein turnover. The proteolytic core of Clp comprises subunits from one plastid‐encoded gene ( clpP1 ) and multiple nuclear genes. The clpP1 gene is highly conserved across most green plants, but it is by far the fastest evolving plastid‐encoded gene in some angiosperms. To better understand these extreme and mysterious patterns of divergence, we investigated the history of clpP1 molecular evolution across green plants by extracting sequences from 988 published plastid genomes. We find that clpP1 has undergone remarkably frequent bouts of accelerated sequence evolution and architectural changes (e.g. a loss of introns and RNA ‐editing sites) within seed plants. Although clpP1 is often assumed to be a pseudogene in such cases, multiple lines of evidence suggest that this is rarely true. We applied comparative native gel electrophoresis of chloroplast protein complexes followed by protein mass spectrometry in two species within the angiosperm genus Silene , which has highly elevated and heterogeneous rates of clpP1 evolution. We confirmed that clpP1 is expressed as a stable protein and forms oligomeric complexes with the nuclear‐encoded Clp subunits, even in one of the most divergent Silene species. Additionally, there is a tight correlation between amino acid substitution rates in clpP1 and the nuclear‐encoded Clp subunits across a broad sampling of angiosperms, suggesting continuing selection on interactions within this complex.
The tribe Jacarandeae includes
Jacaranda(49 species) and Digomphia(3 species), two genera of trees and woody shrubs with Neotropical distribution. Jacarandeae is sister to the rest of the Bignoniaceae, but not much is known about interspecific and intergeneric relationships within this group. Methods
We reconstructed the phylogeny of Jacarandeae using chloroplast (
ndhF, rpl32‐ trnL, trnL‐F) and nuclear ( ETS, PPR62) markers. Evolutionary relationships within Jacarandeae were inferred using Bayesian, Maximum Likelihood, and species tree approaches. The resulting phylogenetic framework was used as the basis to interpret the evolution of key morphological character states (i.e., stamen and calyx traits) and revise the infra‐generic classification of the group. Results Jacarandaand Digomphiabelong to a well‐supported clade, with Digomphianested within Jacaranda. We propose the necessary taxonomic changes to recognize monophyletic taxa, including a broadly circumscribed Jacarandadivided into four sections: (1) Jacarandasect. Nematopogon, species previously included in Digomphiaand united by divided staminode apices and spathaceous calyces; (2) Jacarandasect. Copaia, species with monothecal anthers and cupular calyces; (3) Jacarandasect. Jacaranda, species with monothecal anthers and campanulate calyces; and (4) Jacarandasect. Dilobos, species with dithecal anthers and cupular calyces, and including more than half of the species of the genus, all restricted to Brazil. Conclusions
As circumscribed here, Jacarandeae includes only a broadly defined
Jacarandadivided into four sections. Each section is defined by a unique combination of anther and calyx morphologies.
In plants, 24 nucleotide long heterochromatic si
RNAs (het‐si RNAs) transcriptionally regulate gene expression by RNA‐directed DNAmethylation (Rd DM). The biogenesis of most het‐si RNAs depends on the plant‐specific RNApolymerase IV(Pol IV), and ARGONAUTE4 ( AGO4) is a major het‐si RNAeffector protein. Through genome‐wide analysis of sRNA‐seq data sets, we found that is required for the accumulation of a small subset of het‐si AGO4 RNAs. The accumulation of ‐dependent het‐si AGO4 RNAs also requires several factors known to participate in the effector portion of the Rd DMpathway, including RNA POLYMERASEV ( POLV), DOMAINS REARRANGED METHYLTRANSFERASE2 ( DRM2) and SAWADEE HOMEODOMAIN HOMOLOGUE1 ( SHH1). Like many AGOproteins, AGO4 is an endonuclease that can ‘slice’ RNAs. We found that a slicing‐defective AGO4 was unable to fully recover dependent het‐si AGO4‐ RNAaccumulation from ago4mutant plants. Collectively, our data suggest that ‐dependent si AGO4 RNAs are secondary si RNAs dependent on the prior activity of the Rd DMpathway at certain loci.
NLR‐receptor RPP7 mediates race‐specific immunity in Arabidopsis. Previous screens for enhanced downy mildew( edm) mutants identified the co‐chaperone SGT1b ( EDM1) and the PHD‐finger protein EDM2 as critical regulators of RPP7. Here, we describe a third edmmutant compromised in immunity, RPP7 edm3. encodes a nuclear‐localized protein featuring an EDM3 RNA‐recognition motif. Like EDM2, EDM3 promotes histone H3 lysine 9 dimethylation (H3K9me2) at . Global profiling of H3K9me2 showed RPP7 EDM3 to affect this silencing mark at a large set of loci. Importantly, both EDM3 and EDM2 co‐associate in vivowith H3K9me2‐marked chromatin and transcripts at a critical proximal polyadenylation site of , where they suppress proximal transcript polyadeylation/termination. Our results highlight the complexity of plant RPP7 NLRgene regulation, and establish a functional and physical link between a histone mark and NLR‐transcript processing.