Insights into root development from Arabidopsis root mutants

The root provides a useful system for the analysis of plant organ formation. Mutations that affect root development and physiology have been identified in Arabidopsis thaliana. Affected processes include embryonic root formation, cell expansion, cell differentiation and response to environmental stimuli. Analysis of these mutations is providing insight into fundamental questions of plant development.     

Insights into the function of PsbR protein in Arabidopsis thaliana

The functional state of the Photosystem (PS) II complex in Arabidopsis psbR T-DNA insertion mutant was studied. The DeltaPsbR thylakoids showed about 34% less oxygen evolution than WT, which correlates with the amounts of PSII estimated from Y(D)(ox) radical EPR signal. The increased time constant of the slow phase of flash fluorescence (FF)-relaxation and upshift in the peak position of the main TL-bands, both in the presence and in the absence of DCMU, confirmed that the S(2)Q(A)(-) and S(2)Q(B)(-) charge recombinations were stabilized in DeltaPsbR thylakoids. Furthermore, the higher amount of dark oxidized Cyt-b559 and the increased proportion of fluorescence, which did not decay during the 100s time span of the measurement thus indicating higher amount of Y(D)(+)Q(A)(-) recombination, pointed to the donor side modifications in DeltaPsbR. EPR measurements revealed that S(1)-to-S(2)-transition and S(2)-state multiline signal were not affected by mutation. The fast phase of the FF-relaxation in the absence of DCMU was significantly slowed down with concomitant decrease in the relative amplitude of this phase, indicating a modification in Q(A) to Q(B) electron transfer in DeltaPsbR thylakoids. It is concluded that the lack of the PsbR protein modifies both the donor and the acceptor side of the PSII complex.     

Insights into miRNA regulation of the human glycome

Glycosylation is an intricate process requiring the coordinated action of multiple proteins, including glycosyltransferases, glycosidases, sugar nucleotide transporters and trafficking proteins. Work by several groups points to a role for microRNA (miRNA) in controlling the levels of specific glycosyltransferases involved in cancer, neural migration and osteoblast formation. Recent work in our laboratory suggests that miRNA are a principal regulator of the glycome, translating genomic information into the glycocode through tuning of enzyme levels. Herein we overlay predicted miRNA regulation of glycosylation related genes (glycogenes) onto maps of the common N-linked and O-linked glycan biosynthetic pathways to identify key regulatory nodes of the glycome. Our analysis provides insights into glycan regulation and suggests that at the regulatory level, glycogenes are non-redundant.     

Insights into the phylogeny of systematically controversial haptorian ciliates (Ciliophora, Litostomatea) based on multigene analyses

The ciliate subclass Haptoria is a diverse taxon that includes most of the free-living predators in the class Litostomatea. Phylogenetic study of this group was initially conducted using a single molecular marker small-subunit ribosomal RNA (SSU rRNA genes). Multi-gene analysis has been limited because very few other sequences were available. We performed phylogenetic analyses of Haptoria incorporating new SSU rRNA gene sequences from several debated members of the taxon, in particular, the first molecular data from Cyclotrichium. We also provided nine large-subunit ribosomal RNA (LSU rRNA) gene sequences and 10 alpha-tubulin sequences from diverse haptorians, and two possible relatives of controversial haptorians (Plagiopylea, Prostomatea). Phylogenies inferred from the different molecules showed the following: (i) Cyclotrichium and Paraspathidium were clearly separated from the haptorids and even from class Litostomatea, rejecting their high-level taxonomic assignments based on morphology. Both genera branch instead with the classes Plagiopylea, Prostomatea and Oligohymenophora. This raises the possibility that the well-known but phylogenetically problematic cyclotrichiids Mesodinium and Myrionecta may also have affinities here, rather than with litostomes; (ii) the transfer of Trachelotractus to Litostomatea is supported, especially by the analyses of SSU rRNA and LSU rRNA genes, however, Trachelotractus and Chaenea (more uncertainly) generally form the two deepest lineages within litostomes; and (iii) phylogenies of the new molecular markers are consistent with SSU rRNA gene information in recovering order Pleurostomatida as monophyletic. However, Pleurostomatida branches cladistically within order Haptorida, as does subclass Trichostomatia (on the basis of SSU rRNA phylogenies). Our results suggest that the class-level taxonomy of ciliates is still not resolved, and also that a systematic revision of litostomes is required, beginning at high taxonomic levels (taxa currently ranked as subclasses and orders).