Effects of Adaptation to Elevated Salinity on Some Enzymes' Salt_tolerance in Vitro and Physiological Changes of Eelgrass

The eelgrass ( Zostera marina L.) was treated with artificial seawater (ASW) of different salinities ( 100%, 150% and 200% seawater) for 5 d. The activities of two enzymes extracted from the plant leaves were determined under a salinity grade in vitro So were the photosynthesis rates of the plants from the three treatments in the media with different salinities 100%, 150%, 200%, 300% ASW) and Some physiological data. The data showed that under increased salinities (concentrated seawater), Na+, Cl-, MDA (malon dialdehyde) and glucose contents and the osmotic potentials ( absolute value) in the leaves increased with the salinity elevation in the medium (ASW), but both K+ and free amino acid (mainly proline) contents decreased. Malate dehydrogenase (MDH) from the plant leaves under a salinity grade showed its activities (A) as follows: A(100%) (ASW) > A(150%) (ASW) > A(200%) (ASW). Phosphoenolpyruvate carboxylase (PEPC) extracted from the 100% ASW- and 200% ASW-treated plants showed similar activities (both insensitive to salinities) under the salinity grade in vitro, but the activities of PEPC from plants treated with 150% ASW were dependent oil salinity. Whether the plant is stressed at 150% ASW and can stand higher salinity than seawater needs to be studied further. Meantime, die data do not agree with the opinion that the adaptation of the eelgrass to seawater salinity is partly fulfilled by its insensitiveness to salinities in Some metabolic enzymes. It can be inferred that the lack of transpiration may be an important aspect of tire plant's tolerance to seawater salinity.

The genome of the recretohalophyte Limonium bicolor provides insights into salt gland development and salinity adaptation during terrestrial evolution

Halophytes have evolved specialized strategies to cope with high salinity.The extreme halophyte sea lavender(Limonium bicolor)lacks trichomes but possesses salt glands on its epidermis that can excrete harmful ions,such as sodium,to avoid salt damage.Here,we report a high-quality,2.92-Gb,chromosome-scale L.bicolor genome assembly based on a combination of Illumina short reads,single-molecule,real-time long reads,chromosome conformation capture(Hi-C)data,and Bionano genome maps,greatly enriching the genomic information on recretohalophytes with multicellular salt glands.Although the L.bicolor genome contains genes that show similarity to trichome fate genes from Arabidopsis thaliana,it lacks homologs of the decision fate genes GLABRA3,ENHANCER OF GLABRA3,GLABRA2,TRANSPARENT TESTA GLABRA2,and SIAMESE,providing a molecular explanation for the absence of trichomes in this species.We identified key genes(LbHLH and LbTTG1)controlling salt gland development among classical trichome homologous genes and confirmed their roles by showing that their mutations markedly disrupted salt gland initiation,salt secretion,and salt tolerance,thus offering genetic support for the long-standing hypothesis that salt glands and trichomes may share a common origin.In addition,a whole-genome duplication event occurred in the L.bicolor genome after its divergence from Tartary buckwheat and may have contributed to its adaptation to high salinity.The L.bicolor genome resource and genetic evidence reported in this study provide profound insights into plant salt tolerance mechanisms that may facilitate the engineering of salt-tolerant crops.

A New Approach to Select Doubled Haploid Rice Lines under Salinity Stress Using Indirect Selection Index

This study determined the indirect selection index of doubled haploid(DH)rice using a multivariate analysis approach to select lines adaptive to salinity stress,comprising three experiments.The first experiment involved the selection of good agronomic characters in a field experiment conducted at an experimental station in Bogor,Indonesia.The second experiment involved salinity tolerance screening through hydroponic cultures using 0 and 120 mmol/L NaCl,conducted at a greenhouse in Bogor.The third experiment involved the validation of the indirect adaptability selection index(IASI)through a field experiment in Sukra(saline area).Field experiments followed a randomized complete block design(RCBD),whereas an RCBD nested factorial design was used for the greenhouse experiment.The first and second experiments used 56 DH lines and four check varieties with three replications.In the second experiment,Pokkali and IR29 varieties were also added as tolerant and sensitive checks of salinity,respectively.The third experiment used 28 selected DH lines,Inpari 29 and one sensitive DH line.The good agronomic index(GAI)was 0.465 yield+0.433 number of productive tillers+0.31 number of filled grains.This generated 24 DH rice lines with good agronomic traits.The salinity tolerance index(SaTI)was developed through the average of standardized salinity tolerance score and salinity selection index based on discriminant analysis.This generated 34 DH rice lines with good salinity stress tolerance.The IASI(IASI=GAI–SaTI)selected 28 DH rice lines adaptive to salinity stress and it was considered effective by Sukra validation.

ORF355 confers enhanced salinity stress adaptability to S-type cytoplasmic male sterility maize by modulating the mitochondrial metabolic homeostasis

Moderate stimuli in mitochondria improve wideranging stress adaptability in animals, but whether mitochondria play similar roles in plants is largely unknown. Here, we report the enhanced stress adaptability of S-type cytoplasmic male sterility(CMS-S) maize and its association with mild expression of sterilizing gene ORF355. A CMS-S maize line exhibited superior growth potential and higher yield than those of the near-isogenic N-type line in saline fields. Moderate expression of ORF355 induced the accumulation of reactive oxygen species and activated the cellular antioxidative defense system. This adaptive response was mediated by elevation of the nicotinamide adenine dinucleotide concentration and associated metabolic homeostasis. Metabolome analysis revealed broad metabolic changes in CMS-S lines, even in the absence of salinity stress. Metabolic products associated with amino acid metabolism and galactose metabolism were substantially changed, which underpinned the alteration of the antioxidative defense system in CMS-S plants. The results reveal the ORF355-mediated superior stress adaptability in CMS-S maize and might provide an important route to developing salt-tolerant maize varieties.

Growth,serum biochemical parameters,salinity tolerance and antioxidant enzyme activity of rainbow trout(Oncorhynchus mykiss)in response to dietary taurine levels

This study evaluated the effect of dietary taurine levels on growth,serum biochemical parameters,salinity adaptability,and antioxidant activity of rainbow trout(Oncorhynchus mykiss).Four diets were formulated with taurine supplements at 0,0.5,1,and 2%w/v(abbreviated as To,T05,Tt,and T2,respectively).Rainbow trouts(initial weight of 80.09±4.72 g)were stocked in tanks(180 L capacity),and were fed these diets for six weeks and subsequently underwent salinity acclimation.Physiological indicators were determined before salinity acclimation at 1,4,7,and 14 days afterwards.Results showed that there were no significant differences in growth performance(final mean weight ranged from 182.35 g to 198.48 g;percent weight gain was between 127.68%and 147.92%)of rainbow trout in freshwater stage,but dietary taurine supplement significantly increased serum-free taurine content.After entering seawater,the Na+-K+-ATPase activity of T2 group returned to its freshwater levels,and the serum cortisol content was significantly higher than To and To 5 groups.At the end of this experiment,the liver superoxide dismutase activity in the To and To 5 groups was significantly lower than in the Tj and T2 groups,and the liver catalase in the To group was the lowest whereas that in the T2 group was the highest.Muscle malondialdehyde content was the highest in the To group,and the lowest in the T2 group.Based on the results of this study,supplement of dietary taurine(0.5-2%)enhanced the salinity tolerance in rainbow trout,which increased with the higher taurine concentration.

Neocosmopolitan distributions of invertebrate aquatic invasive species due to euryhaline geographic history and human-mediated dispersal:Ponto-Caspian versus other geographic origins

Background:Aquatic invertebrate species that have broad salinity tolerances may be pre-adapted for invasion success and biogeographic distributional range expansions,facilitated by human-mediated dispersal(HMD),leading to a trend to become neocosmopolitan across many regions of the world.This pattern appears to characterize many Ponto-Caspian(P-C)aquatic invertebrates,which have a>100-year history as aquatic invasive species(AIS),spreading throughout much of Eurasia and for some,in North America and beyond.Our study compiles comparative salinity conditions and distributional data for AIS invertebrate species globally versus those originating from the P-C region,to test whether they statistically differ.Results:Our investigation discerns that a total of 1861 invertebrate AIS taxa have been recorded worldwide,with(A)70.5%exclusively living in the saline adaptive zone of brackish(0.5-30 ppt;A1)and/or marine waters(>30 ppt;A2),(B)20%in the freshwater adaptive zone alone(0-0.5 ppt),(C)7.5%being euryhaline(across both A and B),and(D)2%being semi-aquatic in either(D1)freshwater/terrestrial or(D2)saline/terrestrial environments.In contrast,our results indicate the following proportions for AIS invertebrates of P-C origins:(A)27%exclusively inhabit the saline adaptive zone,(B)25%are entirely freshwater,(C)45%are euryhaline,and(D)3%are semi-aquatic,significantly differing from the global pattern.Euryhaline AIS native to the P-C region thus markedly outnumber(45%)those originating from other regions(7.5%),likely pre-adapting them for widespread establishment in harbors,estuaries,and coastal areas.Moreover,most P-C invertebrate AIS(70%)contain freshwater-tolerant populations(B+C),rendering them very successful invaders of inland water bodies.These broad salinity tolerances of P-C AIS underlie their tremendous invasion successes and growing neocosmopolitan distributions with HMD.Conclusions:An evolutionary and recent history of broad salinity tolerances of a large proportion of P-C invertebrates appears to enhance their ability to invade,establish,and spread in new regions,especially harbors,estuaries,and freshwaters,leading to their increasing neocosmopolitan distributions.This trend likely will continue-accelerating with climate change and increased global transportation-meriting worldwide conservation agency focus and cooperation,along with public education programs aimed to rapidly identify and circumvent new introductions and spread.