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The Tic22 protein was previously identified in pea as a putative component of the chloroplast protein import apparatus. It is a peripheral protein of the inner envelope membrane, residing in the intermembrane space. In Arabidopsis, there are two Tic22 homologues, termed atTic22-III and atTic22-IV, both of which are predicted to localize in chloroplasts. These two proteins defined clades that are conserved in all land plants, which appear to have evolved at a similar rates since their separation >400 million years ago, suggesting functional conservation. The atTIC22-IV gene was expressed several-fold more highly than atTIC22-III, but the genes exhibited similar expression profiles and were expressed throughout development. Knockout mutants lacking atTic22-IV were visibly normal, whereas those lacking atTic22-III exhibited moderate chlorosis. Double mutants lacking both isoforms were more strongly chlorotic, particularly during early development, but were viable and fertile. Double-mutant chloroplasts were small and under-developed relative to those in wild type, and displayed inefficient import of precursor proteins. The data indicate that the two Tic22 isoforms act redundantly in chloroplast protein import, and that their function is non-essential but nonetheless required for normal chloroplast biogenesis, particularly during early plant development.

Species in the ivesioid clade of Potentilla (Rosaceae) are endemic to western North America, an area that underwent widespread aridification during the global temperature decrease following the Mid-Miocene Climatic Optimum. Several morphological features interpreted as adaptations to drought are found in the clade, and many species occupy extremely dry habitats. Recent phylogenetic analyses have shown that the sister group of this clade is Potentilla section Rivales, a group with distinct moist habitat preferences. This has led to the hypothesis that the ivesioids (genera Ivesia, Horkelia and Horkeliella) diversified in response to the late Tertiary aridification of western North America. We used phyloclimatic modeling and a fossil-calibrated dated phylogeny of the family Rosaceae to investigate the evolution of the ivesioid clade. We have combined occurrence- and climate data from extant species, and used ancestral state reconstruction to model past climate preferences. These models have been projected into paleo-climatic scenarios in order to identify areas where the ivesioids may have occurred. Our analysis suggests a split between the ivesioids and Potentilla sect. Rivales around Late Oligocene/Early Miocene (∼23 million years ago, Ma), and that the ivesioids then diversified at a time when summer drought started to appear in the region. The clade is inferred to have originated on the western slopes of the Rocky Mountains from where a westward range expansion to the Sierra Nevada and the coast of California took place between ∼12-2 Ma. Our results support the idea that climatic changes in southwestern North America have played an important role in the evolution of the local flora, by means of in situ adaptation followed by diversification.

The mammalian tick-borne flavivirus group (MTBFG) contains viruses associated with important human and animal diseases such as encephalitis and hemorrhagic fever. In contrast to mosquito-borne flaviviruses where recombination events are frequent, the evolutionary dynamic within the MTBFG was believed to be essentially clonal. This assumption was challenged with the recent report of several homologous recombinations within the Tick-borne encephalitis virus (TBEV). We performed a thorough analysis of publicly available genomes in this group and found no compelling evidence for the previously identified recombinations. However, our results show for the first time that demonstrable recombination (i.e., with large statistical support and strong phylogenetic evidences) has occurred in the MTBFG, more specifically within the Louping ill virus lineage. Putative parents, recombinant strains and breakpoints were further tested for statistical significance using phylogenetic methods. We investigated the time of divergence between the recombinant and parental strains in a Bayesian framework. The recombination was estimated to have occurred during a window of 282 to 76 years before the present. By unravelling the temporal setting of the event, we adduce hypotheses about the ecological conditions that could account for the observed recombination.