Plants are exposed to a variety of abiotic stresses in nature and exhibit unique and complex responses to these stresses depending on their degree of plasticity involving many morphological, cellular, anatomical, and physiological changes. Phytohormones are known to play vital roles in the ability of plants to acclimatize to varying environments, by mediating growth, development, source/sink transitions and nutrient allocation. These signal molecules are produced within the plant, and also referred as plant growth regulators. Although plant response to salinity depends on several factors; nevertheless, phytohormones are thought to be the most important endogenous substances that are critical in modulating physiological responses that eventually lead to adaptation to salinity. Response usually involves fluctuations in the levels of several phytohormones, which relates with changes in expression of genes involved in their biosynthesis and the responses they regulate. Present review described the potential role of different phytohormones and their balances against salinity stress and summarized the research progress regarding plant responses towards salinity at physiological and molecular levels. We emphasized the role of abscisic acid, indole acetic acid, cytokinins, gibberellic acid, salicylic acid, brassinosteroids, jasmonates, ethylene and triazoles in mediating plant responses and discussed their crosstalk at various baseline pathways transduced by these phytohormones under salinity. Current progress is exemplified by the identification and validation of several significant genes that enhanced crops tolerance to salinity, while missing links on different aspects of phytohormone related salinity tolerance are pointed out. Deciphering mechanisms by which plant perceives salinity and trigger the signal transduction cascades via phytohormones is vital to devise salinity related breeding and transgenic approaches.

Phytohormones and plant responses to salinity stress: a review

Sodium chloride toxicity and the cellular basis of salt tolerance in halophytes

Fungi are an understudied, biotechnologically valuable group of organisms. Due to 
the immense range of habitats that fungi inhabit, and the consequent need to compete against a diverse array of other fungi, bacteria, and animals, fungi have developed numerous survival mechanisms. The unique attributes of fungi thus herald great promise for their application in biotechnology and industry. Moreover, fungi can be grown with relative ease, making production at scale viable. The search for fungal biodiversity, and the construction of a living fungi collection, both have incredible economic potential in locating organisms with novel industrial uses that will lead to novel products. This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology. We provide notes and examples for each potential exploitation and give examples from our own work and the work of other notable researchers. We also provide a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products. Fungi have provided the world with penicillin, lovastatin, and other globally significant medicines, and they remain an untapped resource with enormous industrial potential.

The amazing potential of fungi: 50 ways we can exploit fungi industrially

The dominance of salt water across the surface of the earth has lead to the widespread occurrence of salt-affected soils. Salt-tolerant plants (halophytes) have evolved to grow on these soils, with halophytes and less tolerant plants showing a wide range of adaptations. However, most of our crops are salt-sensitive. Consequently, salinity is an ever-present threat to agriculture, especially in areas where secondary salinisation has developed through irrigation or deforestation. Attempts to improve the salt tolerance of crops have met with very limited success, due to the complexity of the trait, both genetically and physiologically. Tolerance shows all the characteristics of a multigenic trait, with quantitative trait loci (QTLs) identified in barley, citrus, rice and tomato. Attempts to produce salt-tolerant crops have involved both the domestication of halophytes and the manipulation of existing crop species through conventional breeding programmes, the use of in vitro selection, pooling physiological traits, interspecific hybridisation, the use of marker-aided selection and the development of transgenic plants. After 10 years of research, the value of using transgenic plants to alter salt tolerance has yet to be tested in the field. The use of physiological traits in breeding programmes and the domestication of halophytes currently offer viable alternatives to the development of tolerance through the use of transgenic technologies.

Why does salinity pose such a difficult problem for plant breeders

Effects of salt stress on rice growth, development characteristics, and the regulating ways: A review

Fil: Devinar, Maria Genoveva. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquimicas y Naturales. Departamento de Biologia Molecular. Laboratorio de Fisiologia Vegetal; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba; Argentina

Different relative humidity conditions combined with chloride and sulfate salinity treatments modify abscisic acid and salicylic acid levels in the halophyte Prosopis strombulifera

Role of abscisic acid in legumes under abiotic stress

Salinity is 
one of the major abiotic stresses that adversely affect the crop productivity and growth of the whole plant. The halophytic Prosopis strombulifera (Fabaceae) shrub is a useful plant model to study the molecular and physiological mechanisms involved in salinity tolerance. In this work, the isolation and characterization of the mRNA for a new atypical LEA protein (PsLEA3) is reported. PsLEA3 has alanine as the most abundant amino acid followed by serine. This characteristic is different from typical LEA proteins which have high glycine content. PsLEA3 shows a negative average of hydropathy and remains localized in the chloroplast. The phylogenetic relationship between related LEA proteins and PsLEA3 showed that this protein belongs to the same group as a LEA protein of Arabidopsis. Northern analysis revealed a differential expression of this atypical LEA mRNA in P. strombulifera plants under NaCl and Na2SO4 treatments. Over-expression in roots of Na2SO4-treated plants from Ψo −1.9 MPa was associated with abscisic acid (ABA) and its conjugate (ABA-glucose ester) accumulation as well as with the root length of these plants, showing an inhibition and toxicity induced by sulphate anion present in the medium.

Isolation of a gene encoding a novel atypical LEA protein from the halophyte Prosopis strombulifera with a sodium salt-specific expression

Prosopis genus is an important member of semiarid, arid and saline environments around the world. This genus includes shrubs and trees that exhibit a high economic and ecological potential in different American regions. These plants are considered to be unique terrestrial species due to their combined ability to fix nitrogen and grow under high-salinity conditions. The South American halophyte, Prosopis strombulifera (Lam) Benth, is distributed from the Arizona desert (U.S.A.) to Patagonia (Argentina) and is especially abundant in the salinized areas of central Argentina. The soil of these areas is characterized by similar proportions of NaCl and Na2SO4. P. strombulifera species showed a halophytic response to NaCl surviving up to 1 M NaCl in in-vitro experiments, but in contrast, a strong growth inhibition at lower Na2SO4 concentrations was observed. These differential responses to the most abundant salts present in salinized soils of Argentina make this species an excellent model to study salt-tolerance mechanisms in halophytic plants. This chapter provides an overview of different salt tolerance mechanisms in the American halophyte Prosopis strombulifera, especially phytohormone pattern, oxidative responses and production of biomolecules. This halophyte may be considered as a new useful genetic source to improve crop salt tolerance and a promising plant as source of natural products for pharmaceutical industry.

Genoveva Devinar

Papers

Different relative humidity conditions combined with chloride and sulfate salinity treatments modify abscisic acid and salicylic acid levels in the halophyte Prosopis strombulifera

Role of abscisic acid in legumes under abiotic stress

Isolation of a gene encoding a novel atypical LEA protein from the halophyte Prosopis strombulifera with a sodium salt-specific expression

Morphophysiology and Biochemistry of Prosopis strombulifera Under Salinity. Are Halophytes Tolerant to All Salts