The Ecophysiological Performance and Traits of Genera within the Stichococcus-like Clade (Trebouxiophyceae) under Matric and Osmotic Stress

Changes in water balance are some of the most critical challenges that aeroterrestrial algae face. They have a wide variety of mechanisms to protect against osmotic stress, including, but not limited to, downregulating photosynthesis, the production of compatible solutes, spore and akinete formation, biofilms, as well as triggering structural cellular changes. In comparison, algae living in saline environments must cope with ionic stress, which has similar effects on the physiology as desiccation in addition to sodium and chloride ion toxicity. These environmental challenges define ecological niches for both specialist and generalist algae. One alga known to be aeroterrestrial and euryhaline is Stichococcus bacillaris Nägeli, possessing the ability to withstand both matric and osmotic stresses, which may contribute to wide distribution worldwide. Following taxonomic revision of Stichococcus into seven lineages, we here examined their physiological responses to osmotic and matric stress through a salt growth challenge and desiccation experiment. The results demonstrate that innate compatible solute production capacity under salt stress and desiccation tolerance are independent of one another, and that salt tolerance is more variable than desiccation tolerance in the Stichococcus-like genera. Furthermore, algae within this group likely occupy similar ecological niches, with the exception of Pseudostichococcus.

Phothochemical quenching is indicative of ionic stress on ‘Tahiti’ acid lime grafted on citrus genotypes

HIGHLIGHTS Salinity increases photochemical heat loss in citrus plants. Genotypes that provide great tolerance lose less energy. ‘Tahiti’ acid lime can be grown under moderate natural salinity when tolerant rootstocks are used.

Ion transporters and their molecular regulation mechanism in plants

With the global population predicted to grow by at least 25% by 2050, the need for sustainable production of nutritious foods is important for human and environmental health. Recent progress demonstrate that membrane transporters can be used to improve yields of staple crops, increase nutrient content and resistance to key stresses, including salinity, which in turn could expand available arable land. Exposure to salt stress affects plant water relations and creates ionic stress in the form of the cellular accumulation of Na+ and Cl- ions. However, salt stress also impacts heavily on the homeostasis of other ions such as Ca2+, K+, and NO3- and therefore requires insights into how transport and compartmentation of these nutrients are altered during salinity stress. Since Na+ interferes with K+ homeostasis, maintaining a balanced cytosolic Na+/K+ ratio has become a key salinity tolerance mechanism. Achieving this homeostatic balance requires the activity of Na+ and K+ transporters and/or channels. The aim of this review is to seek answers to this question by examining the role of major ions transporters and channels in ions uptake, translocation and intracellular homeostasis in plants.

Impact of Betaine Under Salinity on Accumulation of Phenolic Compounds in Safflower (Carthamus tinctorius L.) Sprouts

It has been assumed that abiotic stresses often lead to osmotic and ionic stress in plants either inducing or reducing secondary plant metabolites. Therefore, the influence of NaCl, glycinebetaine (betaine), and NaCl with betaine on the growth and variation in the accumulation of phenolic compounds was investigated in safflower ( Carthamus tinctorius L.). The growth pattern of safflower sprouts was significantly influenced by these treatments. It was found that with increases in the concentration of NaCl, all growth parameters steadily decreased, but growth was markedly increased by adding different concentrations of betaine, especially at 0.5 mM, which produced the highest growth in terms of different growth parameters. High-performance liquid chromatographic (HPLC) analysis revealed changes in 7 different phenolic compounds in response to different treatments. After treatment with up to 200 mM NaCl, the levels of catechin, ferulic acid, benzoic acid, and kaempferol increased, whereas the levels of the remaining phenolic compounds, especially chlorogenic acid, and p-coumaric acid were reduced. Our results suggest that the growth suppression due to salinity stress is decreased in the sprouts of safflower by adding betaine.

A neuroendocrine pathway modulating osmotic stress in Drosophila

Environmental factors challenge the physiological homeostasis in animals, thereby evoking stress responses. Various mechanisms have evolved to counter stress at the organism level, including regulation by neuropeptides. In recent years, much progress has been made on the mechanisms and neuropeptides that regulate responses to metabolic/nutritional stress, as well as those involved in countering osmotic and ionic stresses. Here, we identified a peptidergic pathway that links these types of regulatory functions. We uncover the neuropeptide Corazonin (Crz), previously implicated in responses to metabolic stress, as a neuroendocrine factor that inhibits the release of a diuretic hormone, CAPA, and thereby modulates the tolerance to osmotic and ionic stress. Both knockdown of Crz and acute injections of Crz peptide impact desiccation tolerance and recovery from chill-coma. Mapping of the Crz receptor (CrzR) expression identified three pairs of Capa-expressing neurons (Va neurons) in the ventral nerve cord that mediate these effects of Crz. We show that Crz acts to restore water/ion homeostasis by inhibiting release of CAPA neuropeptides via inhibition of cAMP production in Va neurons. Knockdown of CrzR in Va neurons affects CAPA signaling, and consequently increases tolerance for desiccation, ionic stress and starvation, but delays chill-coma recovery. Optogenetic activation of Va neurons stimulates excretion and simultaneous activation of Crz and CAPA-expressing neurons reduces this response, supporting the inhibitory action of Crz. Thus, Crz inhibits Va neurons to maintain osmotic and ionic homeostasis, which in turn affects stress tolerance. Earlier work demonstrated that systemic Crz signaling restores nutrient levels by promoting food search and feeding. Here we additionally propose that Crz signaling also ensures osmotic homeostasis by inhibiting release of CAPA neuropeptides and suppressing diuresis. Thus, Crz ameliorates stress-associated physiology through systemic modulation of both peptidergic neurosecretory cells and the fat body in Drosophila.

Comparative Transcriptomics Reveals Osmotic and Ionic Stress Key Genes Contributing To Salinity Tolerance Differential in Two Pak Choi Cultivars

Background: Pak choi is an important leafy vegetable crop. Salinity is among the most harmful agents that negatively influence pak choi yield. However, the mechanism of salinity tolerance in pak choi has not been well understood. In this study, the root transcriptomics of two cultivars differing in salinity tolerant, Shanghaijimaocai (S, salinity tolerant) and Te’aiqing (T, salinity sensitive), were investigated under 0 and 100 mM NaCl treatments.Results: Using de novo assembly, 214,952 assembled unigenes were generated. Totals of 6765, 2454, 2451 and 5798 differentially expressed unigenes (DEUs) were identified in comparison of S100/S0, T100/T0, S0/T0 and S100/T100, respectively. Shanghaijimaocai is more sensitive to NaCl stress than Te’aiqing in terms of root transcriptomics. Based on GO and KEGG pathway analysis, several osmotic and ionic stress-related genes including MP3K18, PYL8, PP2C15/16/49, ARF2, bHLH112, bZIP43, COL5, CDF1/3, ERF25/60, HSFA6, MYBS3/59/92/CCA1/PHL5, POD21, GOLS7, CIPK4/7/12, NHX7, SLAH1 and ALMT13, showed higher expression in Shanghaijimaocai than in Te’aiqing. These genes, therefore, might be contributed to the difference in salinity tolerance. Moreover, the physiological shift of peroxidase activity was in accordance with dynamic transcript profile of the relevant unigenes. Conclusions: We determined digital expression profile and discovered a broad survey of unigenes associated with the difference of salinity tolerance between Shanghaijimaocai and Te’aiqing. These findings would be useful for further functional analysis as potential targets to improve resistance to salinity stress via genetic engineering.

Usage of the method of biotechnology in the selection of buckwheat plants in the Far East

Использование селективных сред с высокими концентрациями ионов цинка и меди приводит к индуцированию наиболее значительных генетических различий у регенерантых линий гречихи. При культивировании микропобегов на селективных средах с повышенным содержанием тяжелых металлов установлено, что с увеличением концентрации в питательной среде ионов меди и цинка повышался их ингибирующий эффект. В условиях ионного стресса под действием высоких концентраций меди (184 мг/л) и цинка (404 мг/л) у растений-регенерантов сорта Изумруд содержание рутина увеличилось на 20–22 % по сравнению с контролем. Представленные в статье данные подтверждают перспективность использования в селекции гречихи методов биотехнологии (селективного фактора – сублетальных концентраций ионов меди и цинка в культуре in vitro) для получения новых генотипов с повышенным уровнем стрессоустойчивости и высоким содержанием флавоноидов. The results of molecular genetic studies showed that the usage of selective media with high concentration of zinc and cuprum ions induced the most significant genetic differences among buckwheat regenerative lines. It was found in the process of microshoots cultivation on selective media with high concentration of heavy metals that the inhibiting effect of zinc and cuprum ions produced on plants was enhanced with an increase in their concentration in the nutrient medium. The rutin content in plant-regenerants of Izumrud buckwheat veriety increased by 20–22 % as compared to reference sample under conditions of ionic stress caused by high concentration of cuprum (184 mg/l) and zinc (404 mg/l). The data presented in the article confirm the potential which the usage of the biotechnology method (the selective factor of the sublethal concentrations of zinc and cuprum ions in vitro culture) in the selection of buckwheat plants for the development of new genotypes with high level of stress resilience and flavonoids content.