SCYL2 Genes Are Involved in Clathrin-Mediated Vesicle Trafficking and Essential for Plant Growth.

Protein transport between organelles is an essential process in all eukaryotic cells and is mediated by the regulation of processes such as vesicle formation, transport, docking, and fusion. In animals, SCY1-LIKE2 (SCYL2) binds to clathrin and has been shown to play roles in trans-Golgi network-mediated clathrin-coated vesicle trafficking. Here, we demonstrate that SCYL2A and SCYL2B, which are Arabidopsis ( javax.xml.bind.JAXBElement@6903e0a7 ) homologs of animal SCYL2, are vital for plant cell growth and root hair development. Studies of the SCYL2 isoforms using multiple single or double loss-of-function alleles show that SCYL2B is involved in root hair development and that SCYL2A and SCYL2B are essential for plant growth and development and act redundantly in those processes. Quantitative reverse transcription-polymerase chain reaction and a β-glucuronidase-aided promoter assay show that javax.xml.bind.JAXBElement@3cc2500a and javax.xml.bind.JAXBElement@4b9aa92d are differentially expressed in various tissues. We also show that SCYL2 proteins localize to the Golgi, trans-Golgi network, and prevacuolar compartment and colocalize with Clathrin Heavy Chain1 (CHC1). Furthermore, bimolecular fluorescence complementation and coimmunoprecipitation data show that SCYL2B interacts with CHC1 and two Soluble NSF Attachment Protein Receptors (SNAREs): Vesicle Transport through t-SNARE Interaction11 (VTI11) and VTI12. Finally, we present evidence that the root hair tip localization of Cellulose Synthase-Like D3 is dependent on SCYL2B. These findings suggest the role of SCYL2 genes in plant cell developmental processes via clathrin-mediated vesicle membrane trafficking

Identification and characterization of plant transporters using heterologous expression systems

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Reassessment of tissue Na+ concentration as a criterion for salinity tolerance in bread wheat

The definitive version is available at www.blackwell-synergy.comWheat is the most important crop grown on many of world's saline and sodic soils, and breeding for improved salinity tolerance (ST) is the only feasible way of improving yield and yield stability under these conditions. There are a number of possible mechanisms by which cereals can tolerate high levels of salinity, but these can be considered in terms of Na+ exclusion and tissue tolerance. Na+ exclusion has been the focus of much of the recent work in wheat, but with relatively little progress to date in developing high-yielding, salt-tolerant genotypes. Using a diverse collection of bread wheat germplasm, the present study was conducted to assess the value of tissue Na+ concentration as a criterion for ST, and to determine whether ST differs with growth stage. Two experiments were conducted, the first with 38 genotypes and the second with 21 genotypes. A wide range of Na+ concentrations within the roots and shoots as well as in ST were observed in both experiments. However, maintenance of growth and yield when grown with 100mM NaCl was not correlated with the ability of a genotype to exclude Na+ either from an individual leaf blade or from the whole shoot. The K+:Na+ ratio also showed a wide range among the genotypes, but it did not explain the variation in ST among the genotypes. The results suggested that Na+ exclusion and tissue tolerance varied independently, and there was no significant relationship between Na+ exclusion and ST in bread wheat. Consequently, similar levels of ST may be achieved through different combinations of exclusion and tissue tolerance. Breeding for improved ST in bread wheat needs to select for traits related to both exclusion and tissue tolerance.Yusuf Genc, Glenn K. McDonald, Mark Teste

High Salinity Tolerance in the stl2 Mutation of Ceratopteris richardii is Associated with Enhanced K+ Influx and Loss

The roles of K+ uptake and loss in the salinity response of the wild type and the salt-tolerant mutant stl2 of Ceratopteris richardii were studied by measuring Rb+ influx and loss and the effects of Na+, Mg2+, Ca2+ and K+-transport inhibitors. In addition, electrophysiological responses were measured for both K+ and Rb+ and for the effects of Na+ and NH4+ on subsequent K+-induced depolarizations. stl2 had a 26–40% higher uptake rate for Rb+ than the wild type at 0.5–10 mol m-3 RbCl. Similarly, membrane depolarizations induced by both RbCl and KCl were consistently greater in stl2. In the presence of 0–180 mol m-3 NaCl, stl2 maintained a consistently greater Rb+ influx than the wild type. stl2 retained a greater capacity for subsequent KCl-induced depolarization following exposure to NaCl. Five mol m-3 Mg2+ decreased Rb+ uptake in stl2; however, additional Mg2+ up to 40 mol m-3 did not affect Rb+ uptake further. Ca2+ supplementation resulted in a very minor decrease of Rb+ uptake that was similar in the two genotypes. Tetraethylammonium chloride and CsCl gave similar inhibition of Rb+ uptake in both genotypes, but NH4Cl gave substantially greater inhibition in the wild type than in stl2. NH4Cl resulted in a greater membrane depolarization in the wild type and the capacity for subsequent depolarization by KCl was markedly reduced. stl2 exhibited a higher Independent loss of Rb+ than the wild type, but, in the absence of external K+, loss of Rb+ was equivalent in the two genotypes. Since constitutive K+ contents are nearly identical, we conclude that high K+ influx and loss exact a metabolic cost that is reflected in the inhibition of gametophytic growth. Growth inhibition can be alleviated by reduced supplemental K+ or by treatments that slightly reduce K+ influx, such as moderate concentrations of Na+ or Mg2+. We propose that high throughput of K+ allows maintenance of cytosolic K+ under salt stress and that a high uptake rate for K+ results in a reduced capacity for the entrance and accumulation of alternative cations such as Na+ in the cytosol

The involvement of the transpirational bypass flow in sodium uptake by high- and low-sodium-transporting lines of rice developed through intravarietal selection

We report the characterization of high- and low-sodium-transporting lines developed by intravarietal selection within a cultivar, IR36, of rice (Oryza sativa L.). The purpose was to investigate the mechanistic basis of sodium uptake in material in which differences in salt uptake could be isolated from the many other morphological and physiological characteristics that affect the phenotypic expression of salt tolerance. The lines differed in mean sodium transport by a factor of 2. They differed in vigour and water use efficiency, which are characters that modify the effects of salt transport, by only 12% or 13%. The lines did not differ significantly in other physiological traits that are components of salt resistance: compartmentalization at the leaf and cellular levels. There was a strong correlation between the transport of sodium and a tracer for apoplastic pathways (trisodium, 3-hydroxy-5,8,10-pyrene trisulphonic acid, PTS) in both lines. The regression coefficient for sodium transport on PTS transport was the same in both lines. The individual variation in PTS transport was similar to that in sodium transport, and the variation in the transport of both was very much greater than the variation in any other character studied. The high-sodium-transporting line took up proportionately more PTS than the low-sodium-transporting line. It is concluded that the transpirational bypass flow is of major importance in sodium uptake by rice and that selection for differences in sodium transport has been brought about by selection for heritable differences in the bypass flow