PLANT PHYSIOLOGY And BIOCHEMISTRY

Plant Physiology and Biochemistry publishes original theoretical, experimental and technical contributions in the various fields of plant physiology (biochemistry, physiology, structure, genetics, plant-microbe interactions, etc.) at diverse levels of integration (molecular, subcellular, cellular, organ, whole plant, environmental). Opinions expressed in the journal are the sole responsibility of the authors and publication does not imply the editors' agreement.

PLANT PHYSIOLOGY and BIOCHEMISTRY

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Manuscripts describing molecular-genetic and/or gene expression data that are not integrated with biochemical analysis and/or actual measurements of plant physiological processes are not suitable for PPB. Also "Omics" studies (transcriptomics, proteomics, metabolomics, etc.) reporting descriptive analysis without an element of functional validation assays, will not be considered. Similarly, applied agronomic or phytochemical studies that generate no new, fundamental insights in plant physiological and/or biochemical processes are not suitable for publication in PPB.

Flooding is a major issue for plant survival in many regions of the world. Soil inundation induces multiple plant physiological dysfunctions, leading to a decline in plant growth and survival capacity. Some of the most important effects of flooding include a reduction in water and nutrient uptake and a decrease in metabolism. Prolonged soil flooding will also ultimately lead to anoxia conditions with profound effects on plant respiratory metabolism. However, it is still unclear which signals and which sensory mechanisms are responsible for triggering the plant response. In contrast, it is now established that flooding responses are typified by enhanced ethylene production, accompanied by a signalling cascade which includes a network of hormones and other common secondary signalling molecules. In recent years, there has been significant progress in the understanding of some of the signalling pathways involved during plant stress responses. Here, we present an overview of recent hypothesises on sensing and signalling during plant flooding.

In order to develop a sensitive and reliable method for FFA quantification in lipid matrices of seeds, two SPE procedures employed in meat and dairy chemistry were compared using a 100/1 mixture of triolein/heptadecanoic acid. The overall efficiency of the SPE procedure retained was satisfactory since it allowed removal of 99.8% of triacylglycerols (TAG) and recovery of 99.2% of FFA as quantified by gas chromatography of fatty acid methyl esters (FAME). However, the low amount of TAG eluted in the FFA fraction represented a non-negligible percentage (17%) of FAME and the procedure thus required further improvement. TAG pollution was successively decreased to 12%, 8% and finally 1.5% by: i) modifying the volume of elution of TAG; ii) removing the saponification step initially performed according to the standard FAME procedure; and iii) reducing the duration of the BF(3)-catalyzed methylation reaction to 1 min. The new SPE/methylation procedure described here was then compared to the most widely used method for FFA measurement in plants which is based on thin-layer chromatography (TLC). Both procedures were applied to coffee seeds stored for 0-18 months at 15 degrees C under 62% relative humidity and provided consistent results. A very clear negative correlation was observed between the loss of seed viability and the accumulation of FFA in seeds during the course of storage independent of the method employed for FFA quantification. However, we demonstrated that the TLC/on-silica methylation procedure underestimates FFA contents in comparison with the new SPE/methylation procedure because of a selective loss of unsaturated FA.

Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA which ultimately results in oxidative stress. The ROS comprises both free radical (O(2)(-), superoxide radicals; OH, hydroxyl radical; HO(2), perhydroxy radical and RO, alkoxy radicals) and non-radical (molecular) forms (H(2)O(2), hydrogen peroxide and (1)O(2), singlet oxygen). In chloroplasts, photosystem I and II (PSI and PSII) are the major sites for the production of (1)O(2) and O(2)(-). In mitochondria, complex I, ubiquinone and complex III of electron transport chain (ETC) are the major sites for the generation of O(2)(-). The antioxidant defense machinery protects plants against oxidative stress damages. Plants possess very efficient enzymatic (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX; glutathione reductase, GR; monodehydroascorbate reductase, MDHAR; dehydroascorbate reductase, DHAR; glutathione peroxidase, GPX; guaicol peroxidase, GOPX and glutathione-S- transferase, GST) and non-enzymatic (ascorbic acid, ASH; glutathione, GSH; phenolic compounds, alkaloids, non-protein amino acids and α-tocopherols) antioxidant defense systems which work in concert to control the cascades of uncontrolled oxidation and protect plant cells from oxidative damage by scavenging of ROS. ROS also influence the expression of a number of genes and therefore control the many processes like growth, cell cycle, programmed cell death (PCD), abiotic stress responses, pathogen defense, systemic signaling and development. In this review, we describe the biochemistry of ROS and their production sites, and ROS scavenging antioxidant defense machinery.

Plant physiology and biochemistry make up the backbone of successful horticultural production, and our plant physiology/biochemistry research programs cover a range of areas from whole-plant physiology to plant metabolism and enzymology. Collaborations with faculty in several departments university-wide showcase integrated research projects that address important issues in plant physiology and biochemistry.

Plant Physiology and Biochemistry embraces physiology, biochemistry, molecular biology, biophysics, structure and genetics at different levels, from the molecular to the whole plant and environment.The journal publishes several types of articles: papers, methods, short papers, trends, hypotheses and reviews. Articles for the series: trends, hypotheses and reviews are either invited by the Editors or proposed by authors for the editors' prior agreement. In 1998, the journal published a special issue devoted to ARABIDOPSIS THALIANA.

Plant Physiology and Biochemistry embraces physiology, biochemistry, molecular biology, biophysics, structure and genetics at different levels, from the molecular to the whole plant and environment.The journal publishes several types of articles: papers, methods, short papers, trends, hypotheses and reviews. Articles for the series: trends, hypotheses and reviews are either invited by the Editors or proposed by authors for the editors prior agreement.

Promoting sustainable crop production, improving plant productivity and quality, reducing postharvest losses, understanding how plants sense and respond to abiotic stress, probing the diversity of plant specialized metabolism, and understanding fundamental mechanisms of growth and development

Genetic variations in salt tolerance exist, and the degree of salt tolerance varies with plant species and varieties within a species. Among major crops, barley (Hordeum vulgare) shows a greater degree of salt tolerance than rice (Oryza sativa) and wheat (Triticum aestivum). The degree of variation is even more pronounced in the case of dicotyledons ranging from Arabidopsis thaliana, which is very sensitive towards salinity, to halophytes such as Mesembryanthemum crystallinum, Atriplex sp., Thellungiella salsuginea (previously known as T. halophila) [3, 13, 14]. In the last two decades sumptuous amount of research has been done in order to understand the mechanism of salt tolerance in model plant Arabidopsis [15]. Genetic variations and differential responses to salinity stress in plants differing in stress tolerance enable plant biologists to identify physiological mechanisms, sets of genes, and gene products that are involved in increasing stress tolerance and to incorporate them in suitable species to yield salt tolerant varieties.

Increasing evidence demonstrates the roles of a Salt Overly Sensitive (SOS) stress signalling pathway in ion homeostasis and salt tolerance [24, 25]. The SOS signalling pathway (Figure 1) consists of three major proteins, SOS1, SOS2, and SOS3. SOS1, which encodes a plasma membrane Na+/H+ antiporter, is essential in regulating Na+ efflux at cellular level. It also facilitates long distance transport of Na+ from root to shoot. Overexpression of this protein confers salt tolerance in plants [26, 27]. SOS2 gene, which encodes a serine/threonine kinase, is activated by salt stress elicited Ca+ signals. This protein consists of a well-developed N-terminal catalytic domain and a C-terminal regulatory domain [28]. The third type of protein involved in the SOS stress signalling pathway is the SOS3 protein which is a myristoylated Ca+ binding protein and contains a myristoylation site at its N-terminus. This site plays an essential role in conferring salt tolerance [29]. C-terminal regulatory domain of SOS2 protein contains a FISL motif (also known as NAF domain), which is about 21 amino acid long sequence, and serves as a site of interaction for Ca2+ binding SOS3 protein (Figure 1). This interaction between SOS2 and SOS3 protein results in the activation of the kinase [30]. The activated kinase then phosphorylates SOS1 protein thereby increasing its transport activity which was initially identified in yeast [31]. SOS1 protein is characterised by a long cytosolic C-terminal tail, about 700 amino acids long, comprising a putative nucleotide binding motif and an autoinhibitory domain. This autoinhibitory domain is the target site for SOS2 phosphorylation (Figure 1). Besides conferring salt tolerance it also regulates pH homeostasis, membrane vesicle trafficking, and vacuole functions [32, 33]. Thus with the increase in the concentration of Na+ there is a sharp increase in the intracellular Ca2+ level which in turn facilitates its binding with SOS3 protein. Ca2+ modulates intracellular Na+ homeostasis along with SOS proteins. The SOS3 protein then interacts and activates SOS2 protein by releasing its self-inhibition. The SOS3-SOS2 complex is then loaded onto plasma membrane where it phosphorylates SOS1 (Figure 1). The phosphorylated SOS1 results in the increased Na+ efflux, reducing Na+ toxicity [34]. 041b061a72