Hot off the presses! Apr 01 Trends Plant Sci

The Apr 01 issue of the Trends Plant Sci is now up on Pubget (About Trends Plant Sci): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Editorial Board and Contents
  - Trends Plant Sci 14(4):i (2009)
  
• Erratum: Protein isoprenylation: the fat of the matter: Trends in Plant Science 14 (2009) 3, 163–170
  - Trends Plant Sci 14(4):181 (2009)
  
• Auxin signaling in algal lineages: fact or myth?
  - Trends Plant Sci 14(4):182-188 (2009)
  Auxin is of major importance throughout the life cycle of a plant, affecting several physiological and developmental processes, such as cell expansion and division. However, the evolutionary time point at which auxin became involved in such diverse processes is currently unclear. Despite some controversy, numerous reports demonstrate the presence of auxin in algal lineages and its effects on algal development, suggesting an early evolutionary origin of auxin-dependent mechanisms. Here, we review these reports and discuss in silico analyses of auxin signaling components. It seems that, at least in microalgae, the assumed major components of auxin signaling in land plants are absent. However, these microalgae might have alternative auxin signaling pathways that could account for their responses to auxin.
• A morphogenetic trigger: is there an emerging concept in plant developmental biology?
  - Trends Plant Sci 14(4):189-193 (2009)
  Morphogens are involved in the establishment of positional information that is essential for pattern formation. In plants, the phytohormone auxin displays some characteristics of a morphogen. Gradients of auxin distribution are required for tissue patterning within the embryo and the root apex. In some other instances, such as de novo organogenesis, auxin action can be better described in terms of a morphogenetic trigger, which is defined as a factor that induces, through local increase of its concentration, acquisition of a new developmental fate in plant cells that were originally similar to their neighbours. A morphogenetic trigger specifies the site where a new organ will be formed. In plants, formation of reiterative and modular structures might need the action of both morphogenetic triggers and morphogens.
• Nuclear regulators with a second home in organelles
  - Trends Plant Sci 14(4):194-199 (2009)
  In plants, increasing evidence points towards the existence of nuclear proteins that are also targeted to either mitochondria – a well-known phenomenon from yeast and mammalians – or to plastids. One such protein is Whirly1, which was the first protein to be identified in the nucleus and plastids of the same plant cell. Like Whirly1, most of the dual targeted (nucleus and organelle) proteins have functions in the maintenance of DNA, telomere structuring or gene expression. In some instances, proteins were even shown to be relocated from one compartment to another upon environmental or developmental clues. We hypothesize that one rationale of dual targeting is storage or sequestration of these proteins inside the organelles until specific conditions require their activity in the nucleus.
• Janus-faced charge recombinations in photosystem II photoinhibition
  - Trends Plant Sci 14(4):200-205 (2009)
  Light-induced damage of the photosynthetic apparatus in plants is an important phenomenon that primarily affects the photosystem II complex. Here, we propose a new model of photoinhibition in which charge recombination processes have a double-faced role: first, photodamage is induced by singlet oxygen, which is produced via interaction with the triplet reaction center chlorophyll (3P680) arising from the recombination of the charge-separated state between P680 and the pheophytin electron acceptor (3[P680+Phe−]). Second, photoprotection is provided by competition between 3[P680+Phe−] formation and direct recombination of the 1[P680+Phe−] and P680+QA− states. The efficiency of these two pathways is under control of the redox potential of the Phe and QA electron acceptors, which is utilized during adaptation to high light conditions.
• Thinking outside the F-box: novel ligands for novel receptors
  - Trends Plant Sci 14(4):206-213 (2009)
  The importance of regulated proteolysis in the physiology and development of plants is highlighted by the large number of genes dedicated to proteasome-dependent protein degradation. Within the SCF class of E3 ubiquitin ligases are more than 700 F-box proteins that act as recognition modules to specifically target their dedicated substrates for ubiquitylation. This review focuses on very recent studies indicating that some F-box proteins function as phytohormone or light receptors, which directly perceive signals and facilitate specific target-protein degradation to regulate downstream pathways. If this new connection between ligand-regulated proteolysis and signaling proves to be more extensive, an entirely new way of understanding the control of signal transduction is in the offing.
• The many functions of ERECTA
  - Trends Plant Sci 14(4):214-218 (2009)
  The Arabidopsis thaliana accession Landsberg erecta contains an induced mutation in the leucine-rich repeat receptor-like Ser/Thr kinase gene ERECTA. Landsberg erecta is commonly used as a genetic background in mutant screens and in natural variation studies. Therefore, the erecta mutation is present in many loss-of-function mutants and recombinant inbred lines. Information on how the absence of functional ERECTA affects the interpretation of obtained phenotypic results is scattered. In this report we inventoried ERECTA functions and highlight ERECTA as a pleiotropic regulator of developmental and physiological processes, as well as a modulator of responses to environmental stimuli.
• Singlet oxygen in plants: production, detoxification and signaling
  - Trends Plant Sci 14(4):219-228 (2009)
  Singlet oxygen (1O2) is a singular reactive oxygen species (ROS) that is produced constitutively in plant leaves in light via chlorophylls that act as photosensitizers. This 1O2 production is spatially resolved within thylakoid membranes and is enhanced under light stress conditions. 1O2 can also be produced by phytotoxins during plant–pathogen interactions. 1O2 is highly reactive, can be toxic to cells and can be involved in the signaling of programmed cell death or acclimation processes. Here, we summarize current knowledge on 1O2 management in plants and on the biological effects of this peculiar ROS. Compared with other ROS, 1O2 has received relatively little attention, but recent developments indicate that it has a crucial role in the responses of plants to light.
• Role of plant RNA-binding proteins in development, stress response and genome organization
  - Trends Plant Sci 14(4):229-236 (2009)
  RNA-binding proteins (RBPs) in eukaryotes have crucial roles in all aspects of post-transcriptional gene regulation. They are important governors of diverse developmental processes by modulating expression of specific transcripts. The Arabidopsis (Arabidopsis thaliana) genome encodes for more than 200 different RBPs, most of which are plant specific and are therefore likely to perform plant-specific functions. Indeed, recent identification and analysis of plant RBPs clearly showed that, in addition to the important role in diverse developmental processes, they are also involved in adaptation of plants to various environmental conditions. Clearly, they act by regulating pre-mRNA splicing, polyadenylation, RNA stability and RNA export, as well as by influencing chromatin modification.