Differences in proton pumping and Na/H exchange at the leaf cell tonoplast between a halophyte and a glycophyte

The tonoplast Na+/H+ antiporter and tonoplast H+ pumps are essential components of salt tolerance in plants. The objective of this study was to investigate the transport activity of the tonoplast Na+/H+ antiporter and the tonoplast V-H+-ATPase and V-H+-PPase in a highly tolerant salt-accumulating halophyte, Salicornia dolichostachya, and to compare these transport activities with activities in the related glycophyte Spinacia oleracea. Vacuolar membrane vesicles were isolated by density gradient centrifugation, and the proton transport and hydrolytic activity of both H+ pumps were studied. Furthermore, the Na+/H+-exchange capacity of the vesicles was investigated by 9-amino-6-chloro-2-methoxyacridine fluorescence. Salt treatment induced V-H+-ATPase and V-H+-PPase activity in vesicles derived from S. oleracea, whereas V-H+-ATPase and V-H+-PPase activity in S. dolichostachya was not affected by salt treatment. Na+/H+-exchange capacity followed the same pattern, i.e. induced in response to salt treatment (0 and 200 mM NaCl) in S. oleracea and not influenced by salt treatment (10 and 200 mM NaCl) in S. dolichostachya. Our results suggest that S. dolichostachya already generates a high tonoplast H+ gradient at low external salinities, which is likely to contribute to the high cellular salt accumulation of this species at low external salinities. At high external salinities, S. dolichostachya showed improved growth compared with S. oleracea, but V-H+-ATPase, V-H+-PPase and Na+/H+-exchange activities were comparable between the species, which might imply that S. dolichostachya more efficiently retains Na+ in the vacuole

Tissue tolerance: an essential but elusive trait for salt-tolerant crops

For a plant to persist in saline soil, osmotic adjustment of all plant cells is essential. The more salt-tolerant species accumulate Na+ and Cl– to concentrations in leaves and roots that are similar to the external solution, thus allowing energy-efficient osmotic adjustment. Adverse effects of Na+ and Cl– on metabolism must be avoided, resulting in a situation known as ‘tissue tolerance’. The strategy of sequestering Na+ and Cl– in vacuoles and keeping concentrations low in the cytoplasm is an important contributor to tissue tolerance. Although there are clear differences between species in the ability to accommodate these ions in their leaves, it remains unknown whether there is genetic variation in this ability within a species. This viewpoint considers the concept of tissue tolerance, and how to measure it. Four conclusions are drawn: (1) osmotic adjustment is inseparable from the trait of tissue tolerance; (2) energy-efficient osmotic adjustment should involve ions and only minimal organic solutes; (3) screening methods should focus on measuring tolerance, not injury; and (4) high-throughput protocols that avoid the need for control plants and multiple Na+ or Cl- measurements should be developed. We present guidelines to identify useful genetic variation in tissue tolerance that can be harnessed for plant breeding of salt tolerance

A chloroplast retrograde signal, 3’phosphoadenosine 5’-phosphate, acts as a secondary messenger in abscisic acid signaling in stomatal closure and germination

Organelle-nuclear retrograde signaling regulates gene expression, but its roles in specialized cells and integration with hormonal signaling remain enigmatic. Here we show that the SAL1-PAP (3'-phosphoadenosine 5'- phosphate) retrograde pathway interacts with abscisic acid (ABA) signaling to regulate stomatal closure and seed germination in Arabidopsis. Genetically or exogenously manipulating PAP bypasses the canonical signaling components ABA Insensitive 1 (ABI1) and Open Stomata 1 (OST1); priming an alternative pathway that restores ABA-responsive gene expression, ROS bursts, ion channel function, stomatal closure and drought tolerance in ost1-2. PAP also inhibits wild type and abi1-1 seed germination by enhancing ABA sensitivity. PAP-XRN signaling interacts with ABA, ROS and Ca2+; up-regulating multiple ABA signaling components, including lowly-expressed Calcium Dependent Protein Kinases (CDPKs) capable of activating the anion channel SLAC1. Thus, PAP exhibits many secondary messenger attributes and exemplifies how retrograde signals can have broader roles in hormone signaling, allowing chloroplasts to fine-tune physiological responses.Wannarat Pornsiriwong, Gonzalo M Estavillo, Kai Xun Chan, Estee E Tee, Diep Ganguly, Peter A Crisp, Su Yin Phua, Chenchen Zhao, Jiaen Qiu, Jiyoung Park, Miing Tiem Yong, Nazia Nisar, Arun Kumar Yadav, Benjamin Schwessinger, John Rathjen, Christopher I Cazzonelli, Philippa B Wilson, Matthew Gilliham, Zhong-Hua Chen, Barry J Pogso

Reduced tonoplast fast-activating and slow-activating channel activity is essential for conferring salinity tolerance in a facultative halophyte, quinoa

Halophyte species implement a "salt-including" strategy, sequestering significant amounts of Na+ to cell vacuoles. This requires a reduction of passive Na+ leak from the vacuole. In this work, we used quinoa (Chenopodium quinoa) to investigate the ability of halophytes to regulate Na+-permeable slow-activating (SV) and fast-activating (FV) tonoplast channels, linking it with Na+ accumulation in mesophyll cells and salt bladders as well as leaf photosynthetic efficiency under salt stress. Our data indicate that young leaves rely on Na+ exclusion to salt bladders, whereas old ones, possessing far fewer salt bladders, depend almost exclusively on Na+ sequestration to mesophyll vacuoles. Moreover, although old leaves accumulate more Na+, this does not compromise their leaf photochemistry. FV and SV channels are slightly more permeable for K+ than for Na+, and vacuoles in young leaves express less FV current and with a density unchanged in plants subjected to high (400 mM NaCl) salinity. In old leaves, with an intrinsically lower density of the FV current, FV channel density decreases about 2-fold in plants grown under high salinity. In contrast, intrinsic activity of SV channels in vacuoles from young leaves is unchanged under salt stress. In vacuoles of old leaves, however, it is 2- and 7-fold lower in older compared with young leaves in control- and salt-grown plants, respectively. We conclude that the negative control of SV and FV tonoplast channel activity in old leaves reduces Na+ leak, thus enabling efficient sequestration of Na+ to their vacuoles. This enables optimal photosynthetic performance, conferring salinity tolerance in quinoa species

TRESK-like potassium channels in leukemic T cells

In this study, we present patch-clamp characterization of the background potassium current in human lymphoma (Jurkat cells), generated by voltage-independent 16 pS channels with a high (?100-fold) K +/Na+ selectivity. Depending on the background K + channels density, from few per cell up to ?1 open channel per ?m2, resting membrane potential was in the range of -40 to -83 mV, approaching E K = -88 mV. The background K+ channels were insensitive to margotoxin (3 nM), apamine (3 nM), and clotrimazole (1 ?M), high-affinity blockers of the lymphocyte Kv1.3, SKCa2, and IKCa1 channels. The current depended weakly on external pH. Arachidonic acid (20 ?M) and Hg 2+ (0.3-10 ?M) suppressed background K+ current in Jurkat cells by 75-90%. Background K+ current was weakly sensitive to TEA+ (IC50 = 14 mM), and was efficiently suppressed by externally applied bupivacaine (IC50 = 5 ?M), quinine (IC 50 = 16 ?M), and Ba2+ (2 mM). Our data, in particular strong inhibition by mercuric ions, suggest that background K+ currents expressed in Jurkat cells are mediated by TWIK-related spinal cord K+ (TRESK) channels belonging to the double-pore domain K+ channel family. The presence of human TRESK in the membrane protein fraction was confirmed by Western blot analysis. � 2008 Springer-Verlag

<i>Cannabis</i> Extraction Technologies: Impact of Research and Value Addition in Latin America

The Cannabis genus of plants has been widely used in different cultures for various purposes. It is separated into three main species: sativa, indica, and ruderalis. In ancient practices, the plant was used as a multipurpose crop and valued for its fiber, food, and medicinal uses. Since methodologies for the extraction, processing, and identification of components have become available, medical, and food applications have been increasing, allowing potential development in the pharmaceutical and healthy functional food industries. Although the growing legalization and adoption of cannabis for the treatment of diseases are key factors pushing the growth of its market, the biggest challenge is to obtain higher-quality products in a time- and cost-effective fashion, making the process of extraction and separation an essential step. Latin American countries exhibit great knowledge of extraction technologies; nevertheless, it is still necessary to verify whether production costs are economically profitable. In addition, there has been an increase in commercial cannabis products that may or may not be allowed, with or without quality fact sheets, which can pose health risks. Hence, legalization is mandatory and urgent for the rest of Latin American countries. In this article, the phytochemical compounds (cannabinoids, terpenes, and phenolic compounds), the current status of legalization, extraction techniques, and research advances in cannabis in Latin America are reviewed

Revealing mechanisms of salinity tissue tolerance in succulent halophytes: A case study for Carpobrotus rossi

Efforts to breed salt tolerant crops could benefit from investigating previously unexplored traits. One of them is a tissue succulency. In this work, we have undertaken an electrophysiological and biochemical comparison of properties of mesophyll and storage parenchyma leaf tissues of a succulent halophyte species Carpobrotus rosii (“pigface”). We show that storage parenchyma cells of C. rossii act as Na+ sink and possessed both higher Na+ sequestration (298 vs. 215 mM NaCl in mesophyll) and better K+ retention ability. The latter traits was determined by the higher rate of H+‐ATPase operation and higher nonenzymatic antioxidant activity in this tissue. Na+ uptake in both tissues was insensitive to either Gd3+ or elevated Ca2+ ruling out involvement of nonselective cation channels as a major path for Na+ entry. Patch‐clamp experiments have revealed that Caprobrotus plants were capable to downregulate activity of fast vacuolar channels when exposed to saline environment; this ability was higher in the storage parenchyma cells compared with mesophyll. Also, storage parenchyma cells have constitutively lower number of open slow vacuolar channels, whereas in mesophyll, this suppression was inducible by salt. Taken together, these results provide a mechanistic basis for efficient Na+ sequestration in the succulent leaf tissues