Soil salinity is one of the most serious environmental factors that affect crop productivity worldwide. Inevitable global climate change leading to rise in sea water level would exacerbate degradation of irrigation systems and contamination of ground water resources, which render conventional agricultural practices impossible due to the sensitivity of most crops to salinity. Breeding for development of salt-tolerant crop plants has been a major challenge due to the complexity and multigenic control of salt tolerance traits. Halophytes are capable of surviving and thriving under salt at concentrations as high as 5 g/L, by maintaining negative water potential. Physiological and molecular studies have suggested that halophytes, unlike glycophytes, have evolved mechanisms, such as ion homeostasis through ion extrusion and compartmentalization, osmotic adjustments, and antioxidant production for adaptation to salinity. Employment of integrated approaches involving different omics tools would amplify our understanding of the biology of stress response networks in the halophytes. Translation of the knowledge and resources generated from halophyte relatives of crop plants through functional genomics will lead to the development of new breeds of crops that are suitable for saline agriculture.

BackgroundSoil salinity affects growth and yield of crop plants. Plants respond to salinity by physiological and biochemical adjustments through a coordinated regulation and expression of a cascade of genes. Recently, halophytes have attracted attention of the biologists to understand their salt adaptation mechanisms. Spartina alterniflora (smooth cordgrass) is a Louisiana native monocot halophyte that can withstand salinity up to double the strength of sea water. To dissect the molecular mechanisms underlying its salinity adaptation, leaf and root transcriptome of S. alterniflora was sequenced using 454/GS-FLX.ResultsAltogether, 770,690 high quality reads with an average length 324-bp were assembled de novo into 73,131 contigs (average 577-bp long) with 5.9X sequence coverage. Most unigenes (95 %) annotated to proteins with known functions, and had more than 90 % similarity to rice genes. About 28 % unigenes were considered specific to S. alterniflora. Digital expression profiles revealed significant enrichment (P < 0.01) of transporters, vacuolar proton pump members and transcription factors under salt stress, which suggested the role of ion homeostasis and transcriptional regulation in the salinity adaptation of this grass. Also, 10,805 SSRs markers from 9457 unigenes were generated and validated through genetic diversity analysis among 13 accessions of S. alterniflora.ConclusionsThe present study explores the transcriptome of S. alterniflora to understand the gene regulation under salt stress in halophytes. The sequenced transcriptome (control and salt-regulated) of S. alterniflora provides a platform for further gene finding studies in grasses. This study and our previously published studies suggested that S. alterniflora is a rich reservoir of salt tolerance genes that can be used to develop salt tolerant cereal crops, especially rice, a major food crop of global importance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3017-3) contains supplementary material, which is available to authorized users.

Summary Actin‐depolymerizing factors ( ADF s) maintain the cellular actin network dynamics by regulating severing and disassembly of actin filaments in response to environmental cues. An ADF isolated from a monocot halophyte, Spartina alterniflora ( Sa ADF 2 ), imparted significantly higher level of drought and salinity tolerance when expressed in rice than its rice homologue Os ADF 2 . Sa ADF 2 differs from Os ADF 2 by a few amino acid residues, including a substitution in the regulatory phosphorylation site serine‐6, which accounted for its weak interaction with Os CDPK 6 (calcium‐dependent protein kinase), thus resulting in an increased efficacy of Sa ADF 2 and enhanced cellular actin dynamics. Sa ADF 2 overexpression preserved the actin filament organization better in rice protoplasts under desiccation stress. The predicted tertiary structure of Sa ADF 2 showed a longer F‐loop than Os ADF 2 that could have contributed to higher actin‐binding affinity and rapid F‐actin depolymerization in vitro by Sa ADF 2. Rice transgenics constitutively overexpressing Sa ADF 2 ( Sa ADF 2 ‐ OE ) showed better growth, relative water content, and photosynthetic and agronomic yield under drought conditions than wild‐type ( WT ) and Os ADF 2 overexpressers ( Os ADF 2‐ OE ). Sa ADF 2 ‐ OE preserved intact grana structure after prolonged drought stress, whereas WT and Os ADF 2 ‐ OE presented highly damaged and disorganized grana stacking. The possible role of ADF 2 in transactivation was hypothesized from the comparative transcriptome analyses, which showed significant differential expression of stress‐related genes including interacting partners of ADF 2 in overexpressers. Identification of a complex, differential interactome decorating or regulating stress‐modulated cytoskeleton driven by ADF isoforms will lead us to key pathways that could be potential target for genome engineering to improve abiotic stress tolerance in agricultural crops.

The details of a swirl torch ignition system and the evaluation process to determine its capabilities in terms of ignitability limits and combustion range are presented. The torch ignition system was designed as the ignition source for a series of experiments with the purpose of characterizing the properties of methane as they are involved in its performance as a rocket fuel. This is done with putting it on par research-wise with other more widely used fuels, such as hydrogen or monomethylhydrazine[1]. The experimental approach of the project entails the use of GOX/LOX/GCH 4 /LCH 4 due to the proposed benefit of feeding the torch ignition system from the boil-off generated in the main storage tanks, therefore expanding the operational inlet condition range without compromising the system's functionality. The torch ignition system is designed to be integrated into, and serving as the ignition source for, a Multi Purpose Optically Accessible Combustor (MOAC). The objective of this system's development and testing is to obtain the operability limits during ignition and establish the conditions leading to a stable and reliable ignition. This document discusses the iterative design process of the torch ignition system and its parts, the experimental approach to its characterization, and the test results that have been so far analyzed and documented in the form of flammability maps. Nomenclature ṁ = Mass Flow Rate MR = Mixture Ratio