Theoretical and experimental approaches to understand morphogen gradients

Morphogen gradients, which specify different fates for cells in a direct concentration‐dependent manner, are a highly influential framework in which pattern formation processes in developmental biology can be characterized. A common analysis approach is combining experimental and theoretical strategies, thereby fostering relevant data on the dynamics and transduction of gradients. The mechanisms of morphogen transport and conversion from graded information to binary responses are some of the topics on which these combined strategies have shed light. Herein, we review these data, emphasizing, on the one hand, how theoretical approaches have been helpful and, on the other hand, how these have been combined with experimental strategies. In addition, we discuss those cases in which gradient formation and gradient interpretation at the molecular and/or cellular level may influence each other within a mutual feedback loop. To understand this interplay and the features it yields, it becomes essential to take system‐level approaches that combine experimental and theoretical strategies.     

ITN1, a novel gene encoding an ankyrin-repeat protein that affects the ABA-mediated production of reactive oxygen species and is involved in salt-stress tolerance in Arabidopsis thaliana

Salt stress and abscisic acid (ABA) induce accumulation of reactive oxygen species (ROS) in plant cells. ROS not only act as second messengers for the activation of salt-stress responses, but also have deleterious effects on plant growth due to their cytotoxicity. Therefore, the timing and degree of activation of ROS-producing or ROS-scavenging enzymes must be tightly regulated under salt-stress conditions. We identified a novel locus of Arabidopsis, designated itn1 (increased tolerance to NaCl1), whose disruption leads to increased salt-stress tolerance in vegetative tissues. ITN1 encodes a transmembrane protein with an ankyrin-repeat motif that has been implicated in diverse cellular processes such as signal transduction. Comparative microarray analysis between wild-type and the itn1 mutant revealed that induction of genes encoding the ROS-producing NADPH oxidases (RBOHC and RBOHD) under salt-stress conditions was suppressed in the mutant. This suppression was accompanied by a corresponding reduction in ROS accumulation. The ABA-induced expression of RBOHC and RBOHD was also suppressed in the mutant, as was the case for RD29A, an ABA-inducible marker gene. However, the ABA-induced expression of another marker gene, RD22, was not impaired in the mutant. These results suggest that the itn1 mutation partially impairs ABA signaling pathways, possibly leading to the reduction in ROS accumulation under salt-stress conditions. We discuss the possible mechanisms underlying the salt-tolerant phenotype of the itn1 mutant.     

Changes in the specificity of antibodies by site-specific mutagenesis followed by random mutagenesis.

The specificity for 11-deoxycortisol (11-DOC) of a monoclonal antibody (mAb), designated SCET, was changed to specificity for cortisol (CS) by site-specific mutagenesis followed by random mutagenesis. The Fab form of SCET was expressed on the surface of a phage. During the first step, mutations were introduced at 14 amino acid positions in three complementarity-determining regions (CDRs) of the VH domain that seemed likely to form the steroid-binding pocket. A clone, DcC16, was isolated from the resultant library with multiple mutations and this clone was shown to have CS-binding activity but also to retain high 11-DOC-binding activity. During the second step, mutations were introduced randomly into the entire VH-coding region of the DcC16 clone by an error-prone polymerase chain reaction, and CS-specific mutant antibodies were selected in the presence of 11-DOC as a competitor. Three representative clones were analyzed with the BIAcore instrument, and each revealed a large increase in the binding constant for CS and a decrease in that for 11-DOC. Structural models, constructed by computer simulation, indicated the probable molecular basis for these changes in specificity.     

Brassinosteroids Dominate Hormonal Regulation of Plant Thermomorphogenesis via BZR1

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Crop husbandry activities and wild plant gathering,use and consumption at the EPPNB Tell Qarassa North (south Syria)

The Early Pre-Pottery Neolithic B (EPPNB) in southwest Asia is a fundamental period in research on the origins of domesticated plants. However, there are few archaeobotanical data with which to characterise the plant-based subsistence and crop husbandry activities during this time, which hinders the understanding of the factors that triggered the appearance of plant domestication. In this paper, analyses of non-woody plant macro-remains provide new insights into subsistence activities such as crop cultivation (husbandry activities and storage) and plant use (wild plant gathering and food preparation) during the EPPNB at Tell Qarassa North (south Syria). We make comparisons between Tell Qarassa North and the evidence at earlier and later periods as to how plants were used, and highlight similarities and differences in the practices attested, as well as describing some of the consequences that these plant-related activities may have had in terms of labour and social organization during EPPNB.     

Downstream processing of algal polyunsaturated fatty acids

Little information exists on recovering polyunsaturated fatty acids from microalgae; however, methods for concentration and purification of PUFAs from fish oil have been extensively reported. This review examines recovery and purification of microalgae derived PUFAs, but techniques developed for use with fish oil are also reviewed as being potentially useful for concentration and purification from microalgae. The two main techniques for concentrating and purifying-urea fractionation and high performance liquid chromatography-are discussed in depth and attention is focused on the process developed by the authors for obtaining highly pure PUFA. Other potentially useful techniques, such as supercritical fluid extraction and lipase-catalyzed processing are detailed.