In Silico and Biochemical Analysis of Physcomitrella patens Photosynthetic Antenna: Identification of Subunits which Evolved upon Land Adaptation

Background. In eukaryotes the photosynthetic antenna system is composed of subunits encoded by the light harvesting complex (Lhc) multigene family. These proteins play a key role in photosynthesis and are involved in both light harvesting and photoprotection. The moss Physcomitrella patens is a member of a lineage that diverged from seed plants early after land colonization and therefore by studying this organism, we may gain insight into adaptations to the aerial environment. Principal Findings. In this study, we characterized the antenna protein multigene family in Physcomitrella patens, by sequence analysis as well as biochemical and functional investigations. Sequence identification and analysis showed that some antenna polypeptides, such as Lhcb3 and Lhcb6, are present only in land organisms, suggesting they play a role in adaptation to the sub-aerial environment. Our functional analysis which showed that photo-protective mechanisms in Physcomitrella patens are very similar to those in seed plants fits with this hypothesis. In particular, Physcomitrella patens also activates Non Photochemical Quenching upon illumination, consistent with the detection of an ortholog of the PsbS protein. As a further adaptation to terrestrial conditions, the content of Photosystem I low energy absorbing chlorophylls also increased, as demonstrated by differences in Lhca3 and Lhca4 polypeptide sequences, in vitro reconstitution experiments and low temperature fluorescence spectra. Conclusions. This study highlights the role of Lhc family members in environmental adaptation and allowed proteins associated with mechanisms of stress resistance to be identified within this large family

Genetics of superior growth traits in trees are being mapped but will the faster-growing risk-taker make it in the wild?

Increased biomass production of trees is a research field of great contemporary interest. Estimates of future needs for production of fibre, wood and biofuel suggest a need for significantly increased production in forests (Ragauskas et al. 206). This demand can only be met through increased productivity and/or resource utilization efficiency of tree crops. That is, we must explore the potential to optimize the genetic makeup of trees to achieve greater productivity in their growing environments. Since the introduction of molecular biology in plant sciences, the interest in genetic improvement of both agricultural and tree crops has been increasing and is currently one of the most intense areas of plant research. At the same time, tree and stand growth have been studied within (and across) the fields of ecophysiology, ecology, silviculture and forest management. This work has resulted in statistical and process-based models that relate tree growth to availability of various resources, and that thus can inform management (Landsberg and Waring 1997). Process-based growth models have been developed largely independent of the expanding knowledge base in molecular biology and the findings that tree growth can be directly improved through genetic alterations of specific processes such as lignin synthesis, frost hardiness and nitrogen (N) assimilation (Ragauskas et al. 2006, Ye et al. 2011). Similarly, we have underutilized the potential for ecological theories and growth models to guide breeding programmes by predicting the performance of genetically altered trees in the field. This 'Invited issue' is designed to stimulate research targeted at explicitly linking molecular understanding and tools and growth of forest stands