Phosphate (Pi) and its anhydrides constitute
major nodes in metabolism. Thus, plant performance depends directly on
Pi nutrition. Inadequate Pi availability in the rhizosphere is a common
challenge to plants, which activate metabolic and developmental
responses to maximize Pi usage and acquisition. The sensory mechanisms
that monitor environmental Pi and transmit the nutritional signal to
adjust root development have increasingly come into focus. Recent
transcriptomic analyses and genetic approaches have highlighted complex
antagonistic interactions between external Pi and Fe bioavailability and
have implicated the stem cell niche as a target of Pi sensing to
regulate root meristem activity.
Schumann, N.; Navarro-Quezada, A.; Ullrich, K.; Kuhl, C.; Quint, M. Molecular Evolution and Selection Patterns of Plant F-box Proteins with C-terminal Kelch Repeats Plant Physiol 155, 835-850, (2011) DOI: 10.1104/pp.110.166579
The F-box protein superfamily represents one of the largest families in the plant kingdom. F-box proteins phylogenetically organize into numerous subfamilies characterized by their carboxyl (C)-terminal protein-protein interaction domain. Among the largest F-box protein subfamilies in plant genomes are those with C-terminal kelch repeats. In this study, we analyzed the phylogeny and evolution of F-box kelch proteins/genes (FBKs) in seven completely sequenced land plant genomes including a bryophyte, a lycophyte, monocots, and eudicots. While absent in prokaryotes, F-box kelch proteins are widespread in eukaryotes. Nonplant eukaryotes usually contain only a single FBK gene. In land plant genomes, however, FBKs expanded dramatically. Arabidopsis thaliana, for example, contains at least 103 F-box genes with well-conserved C-terminal kelch repeats. The construction of a phylogenetic tree based on the full-length amino acid sequences of the FBKs that we identified in the seven species enabled us to classify FBK genes into unstable/stable/superstable categories. In contrast to superstable genes, which are conserved across all seven species, kelch domains of unstable genes, which are defined as lineage specific, showed strong signatures of positive selection, indicating adaptational potential. We found evidence for conserved protein features such as binding affinities toward A. thaliana SKP1-like adaptor proteins and subcellular localization among closely related FBKs. Pseudogenization seems to occur only rarely, but differential transcriptional regulation of close relatives may result in subfunctionalization.