Identification of quantitative trait loci for the dead leaf rate and the seedling dead rate under alkaline stress in rice

The quantitative trait loci （QTLs） for the dead leaf rate （DLR） and the dead seedling rate （DSR） at the different rice growing periods after transplanting under alkaline stress were identified using an F2：3 population, which included 200 individuals and lines derived from a cross between two japonica rice cultivars Gaochan 106 and Changbai 9 with microsatellite markers. The DLR detected at 20 days to 62 days after transplanting under alkaline stress showed continuous normal or near normal distributions in F3 lines, which was the quantitative trait controlled by multiple genes. The DSR showed a continuous distribution with 3 or 4 peaks and was the quantitative trait controlled by main and multiple genes when rice was grown for 62 days after transplanting under alkaline stress. Thirteen QTLs associated with DLR were detected at 20 days to 62 days after transplanting under alkaline stress. Among these, qDLR9-2 located in RM5786-RM160 on chromosome 9 was detected at 34 days, 41 days, 48 days, 55 days, and 62 days, respectively; qDLR4 located in RM3524-RM3866 on chromosome 4 was detected at 34 days, 41 days, and 48 days, respectively; qDLR7-1 located in RM3859-RM320 on chromosome 7 was detected at 20 days and 27 days; and qDLR6-2 in RM1340-RM5957 on chromosome 6 was detected at 55 days and 62 days, respectively. The alleles of both qDLR9-2 and qDLR4 were derived from alkaline sensitive parent ＂Gaochanl06＂. The alleles of both qDLR7-1 and qDLR6-2 were from alkaline tolerant parent Changbai 9. These gene actions showed dominance and over dominance primarily. Six QTLs associated with DSR were detected at 62 days after transplanting under alkaline stress. Among these, qDSR6-2 and qDSR8 were located in RM1340-RM5957 on chromosome 6 and in RM3752-RM404 on chromosome 8, respectively, which were associated with DSR and accounted for 20.32% and 18.86% of the observed phenotypic variation, respectively; qDSR11-2 and qDSR11-3 were located in RM536-RM479 and RM2596-RM286 on chromosome 11, respectively, which were associated with DSR explaining 25.85% and 15.41% of the observed phenotypic variation, respectively. The marker flanking distances of these QTLs were quite far except that of qDSR6-2, which should be researched further.

RNAi-mediated suppression of the abscisic acid catabolism gene Os ABA8ox1 increases abscisic acid content and tolerance to saline–alkaline stress in rice(Oryza sativa L.)

Saline–alkaline(SA) stress is characterized by high salinity and high alkalinity(high p H), which severely inhibit plant growth and cause huge losses in crop yields worldwide. Here we show that a moderate elevation of endogenous abscisic acid(ABA) levels by RNAi-mediated suppression of Os ABA8 ox1(Os ABA8 ox1-kd), a key ABA catabolic gene, significantly increased tolerance to SA stress in rice plants. We produced Os ABA8 ox1-kd lines in two different japonica cultivars, Dongdao 4 and Nipponbare. Compared with nontransgenic control plants(WT), the Os ABA8 ox1-kd seedlings accumulated 25.9%–55.7% higher levels of endogenous ABA and exhibited reduced plasmalemma injury, ROS accumulation and Na;/K;ratio, and higher survival rates, under hydroponic alkaline conditions simulated by 10, 15, and 20 mmol L-1 of Na;CO;. In pot trials using SA field soils of different alkali levels(p H 7.59, 8.86, and 9.29), Os ABA8 ox1–kd plants showed markedly higher seedling survival rates and more vigorous plant growth, resulting in significantly higher yield components including panicle number(85.7%–128.6%), spikelets per panicle(36.9%–61.9%), branches(153.9%–236.7%), 1000–kernel weight(20.0%–28.6%), and percentage of filled spikelets(96.6%–1340.8%) at harvest time. Under severe SA soil conditions(p H = 9.29, EC = 834.4 μS cm-1),Os ABA8 ox1-kd lines showed an 194.5%–1090.8% increase in grain yield per plant relative to WT plants.These results suggest that suppression of Os ABA8 ox1 to increase endogenous ABA levels provides a new molecular approach for improving rice yield in SA paddies.

Changes in the Vascular Cylinder of Wild Soybean Roots Under Alkaline Stress

Changes in the vascular cylinder of wild soybean （Glycine soja Sieb. et Zucc） roots under alkaline stress were investigated in an experiment that applied 90 mmol L1 alkaline stress for 10 d at the five-trifoliate plant growth stage in Huinan County, Jilin Province, China. Root samples were collected and paraffin-cut sections were made, and the root structure was observed under an optical microscope. There were significant changes in the vascular cylinder of G. soja roots under alkaline stress. Root diameter was reduced and the vascular cylinder changed from tetrarch to triarch pattern. Alkaline stress resulted in reduced, diameters of root vessels, and a large amount of residual, alkaline solution was stained cyaneous in vessels. The paratracheal parenchymatous cells of the vessels were large and there was little secondary xylem. Thus, alkaline stress caused structural changes in the vascular cylinder of G. soja.

Physiological Effects of Alkaline Stress on Seedlings of Lonicera caerulea L.

[Objectives]This study was conducted to clarify the saline-alkali tolerance in seedlings of Lonicera caerulea L.[Methods]The L.caerulea seedling variety,Lanjingling,was used as the test material,and alkaline solution(NaHCO 3)with different concentration gradients was used for stress treatment to observe physiological effects on L.caerulea seedlings.[Results]L.caerulea seedlings were most affected by alkaline stress at a treatment concentration of 100 mmol/L,and their osmotic substances(proline,soluble sugar,soluble protein)and antioxidant enzymes(CAT,SOD and POD)were higher in content at a concentration of 100 mmol/L compared with the alkaline stresses in this range.The contents were generally higher,and even in the detection of proline,soluble sugar,SOD and POD,the contents of these substances and enzymes reached a peak at 100 mmol/L.The contents of soluble sugar,CAT,SOD,POD and malondialdehyde were generally higher than that of the control check(CK),and the contents of proline and soluble protein in each treatment concentration were generally higher than that of the CK.[Conclusions]The metabolic physiology of L.caerulea seedlings has a certain adaptability to alkaline stress.

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test（SSRT） in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking（SCC） behavior of 7003 aluminum alloy（AA7003） in acid and alkaline chloride solutions under various applied potentials（Ea）. The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution（AD） at open-circuit potential（OCP） and is highly susceptible to hydrogen embrittlement（HE） at high negative Ea in the solutions with p H levels of 4 and 11. The susceptibility increases with negative shift in the potential when Ea is less than-1000 m V vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when Ea is equal to-1000 m V vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

Analysis of Organic Acids Accumulated in Kochia Scoparia Shoots and Roots by Reverse-phase High Performance Liquid Chromatography Under Salt and Alkali Stress

Several organic acids accumulated in Kochia Scoparia shoots and roots were studied by means of reverse-phase high performance liquid chromatography with a C18 column. Five types of binary organic acids were separated. The organic acid concentrations were determined in K. Scoparia seedlings stressed by saline （NaCI） and alkaline （NaHCO3） at the same Na^＋ concentration. Concentrations of organic acids are stimulated by alkaline because the cells will adjust their pH values through the accumulation of organic acids, when the environment is basic. The concentrations of oxalic acid and succinic acid are higher than those of other organic acids, including tartaric acid and malic acid, and the concentration of citric acid is the lowest. The concentrations of the organic acids in the roots are higher than those in the shoots under salt（NaCI） stress, but the results are opposite while the roots are under alkali （ NaHCO3 ） stress. This indicates that there are different adaptive strategies for K. Scopar/a seedlings in organic acid metabolism under salt and alkali stress.

An efficient corrosion inhibitor of cassava starch graft copolymer for aluminum in phosphoric acid

Starch is one of the richest natural polymers with low-cost,non-toxic and biodegradable,but is seldom directly used as corrosion inhibitor due to its poor inhibitive ability and low water solubility.To solve this problem,cassava starch-acryl amide graft copolymer(CS-AAGC)was prepared through grafting acryl amide(AA)with cassava starch(CS),and it was firstly examined as an efficient inhibitor for 1060 aluminum in 1.0 mol·L^(-1)H_(3)PO_(4) media.The adsorption behavior of CS-AAGC and its electrochemical mechanism were investigated by weight loss and electrochemical methods.Additionally,the inhibited aluminum surface was fully characterized by a series of SEM,AFM,contact angle measurements and XPS.Results confirm that CS-AAGC performs better inhibitive ability than CS,AA or CS/AA mixture,and the maximum inhibition efficiency of 1.0 g·L^(-1)CS-AAGC is 90.6%at 20℃.CS-AAGC acts as a mixed-type inhibitor while mainly retards the anodic reaction.EIS has three time constants,and the polarization resistance is significantly increased in the presence of CS-AAGC.The micrograph of inhibited aluminum surface is of hydrophobic nature with low surface roughness and little corrosion degree.

Knockout of a gene encoding a Gγ protein boosts alkaline tolerance in cereal crops

Sorghum is highly tolerant to alkaline stress,but the underlying mechanisms are not well understood.Here,based on genotypic difference in alkaline tolerance of sorghum,it was found that AT1(Alkaline tolerance 1)encoding a G protein is involved in alkaline tolerance through negatively modulating the phosphorylation level of PIP2,an aquaporin with transport activity for H_(2)O_(2).Knockout of AT1 releases its inhibition of PIP2,thereby resulting in an increased transport of H_(2)O_(2)from the cytosol into the apoplast,subsequently boosting alkaline tolerance.

The alkaline tolerance in Arabidopsis requires stabilizing microfilament partially through inactivation of PKS5 kinase

High soil pH is harmful to plant growth and development. The organization and dynamics of microfilament （MF） cytoskeleton play important roles in the plant anti-alkaline process. In the previous study, we determined that alkaline stress induces a signal that triggers MF dynamicsdependent root growth. In this study we identified that PKS5 kinase involves in this regulatory process to facilitate the signal to reach the downstream target ME Under pH 8.3 treatment, the depolymerization of MF was faster in pks5-4 （PKS5 kinase constitutively activated） than that in wild-type plants. The inhibition of wild-type, pks5-1, and pks5-4 root growth by pH 8.3 was correlated to their MF depolymerization rate. When the plants were treated with phalloidin to stabilize MF, the high pH sensitive phenotype of pks5-4 can be partially rescued. When the plants were treated with a kinase inhibitor Staurosporine, the MF depolymerization rate in pks5-4 was similar as that in wild-type under pH 8.3 treatment and the sensitivity of root growth was also rescued. However, when the plants were treated with LaC13, a calcium channel blocker, the root growth sensitivity ofpks5-4 under pH 8.3 was rescued but MF depolymerization was even faster than that of plants without LaC13 treatment. These results suggest that the PKS5 involves in external high pH signal mediated MF depolymerization, and that may be independent of calcium signal.

Early Transcriptomic Adaptation to Na_2CO_3 Stress Altered the Expression of a Quarter of the Total Genes in the Maize Genome and Exhibited Shared and Distinctive Profles with NaCl and High pH Stresses

Sodium carbonate （Na2CO3） presents a huge challenge to plants by the combined damaging effects of Na＋, high pH, and CO32. Little is known about the cellular responses to Na2CO3 stress. In this study, the transcriptome of maize （Zea mays L. cv. B73） roots exposed to Na2CO3 stress for 5 h was compared with those of NaCI and NaOH stresses. The expression of 8,319 genes, representing over a quarter of the total number of genes in the maize genome, was altered by Na2CO3 stress, and the downregulated genes （5,232） outnumbered the upregulated genes （3,087）. The effects of Na2CO3 differed from those of NaCI and NaOH, primarily by downregulating different categories of genes. Pathways commonly altered by Na2CO3, NaCI, and NaOH were enriched in phenylpropanoid biosynthesis, oxidation of unsaturated fatty acids, ATP- binding cassette （ABC） transporters, as well as the metabolism of secondary metabolites. Genes for brassinosteroid biosynthesis were specifically upregulated by Na2CO3, while genes involved in ascorbate and aldarate metabolism, protein processing in the endoplasmic reticulum and by N-glycosylation, fatty acid biosynthesis, and the circadian rhythm were downregulated. This work provides the first holistic picture of early transcriptomic adaptation to Na2CO3 stress, and highlights potential molecular pathways that could be manipulated to improve tolerance in maize.

Acetylproteomics analyses reveal critical features of lysine-ε-acetylation in Arabidopsis and a role of 14-3-3 protein acetylation in alkaline response

Lysine-ε-acetylation(Kac)is a post-translational modification(PTM)that is critical for metabolic regulation and cell signaling in mammals.However,its prevalence and importance in plants remain to be determined.Employing high-resolution tandem mass spectrometry,we analyzed protein lysine acetylation in five representative Arabidopsis organs with 2~3 biological replicates per organ.A total of 2887 Kac proteins and 5929 Kac sites were identified.This comprehensive catalog allows us to analyze proteome-wide features of lysine acetylation.We found that Kac proteins tend to be more uniformly expressed in different organs,and the acetylation status exhibits little correlation with the gene expression level,indicating that acetylation is unlikely caused by stochastic processes.Kac preferentially targets evolutionarily conserved proteins and lysine residues,but only a small percentage of Kac proteins are orthologous between rat and Arabidopsis.A large portion of Kac proteins overlap with proteins modified by other PTMs including ubiquitination,SUMOylation and phosphorylation.Although acetylation,ubiquitination and SUMOylation all modify lysine residues,our analyses show that they rarely target the same sites.In addition,we found that“reader”proteins for acetylation and phosphorylation,i.e.,bromodomain-containing proteins and GRF(General Regulatory Factor)/14-3-3 proteins,are intensively modified by the two PTMs,suggesting that they are main crosstalk nodes between acetylation and phosphorylation signaling.Analyses of GRF6/14-3-3λreveal that the Kac level of GRF6 is decreased under alkaline stress,suggesting that acetylation represses plant alkaline response.Indeed,K56ac of GRF6 inhibits its binding to and subsequent activation of the plasma membrane H+-ATPase AHA2,leading to hypersensitivity to alkaline stress.These results provide valuable resources for protein acetylation studies in plants and reveal that protein acetylation suppresses phosphorylation output by acetylating GRF/14-3-3 proteins.