Jasmonic acid is involved in the water-stress-induced betaine accumulation in pear leaves

Jasmonic acid (JA) is known to be involved in the response of plants to environmental stresses such as drought, and betaine (glycinebetaine) is an osmopretectant accumulated in plants under environmental stresses including drought. However, it remains currently unclear whether JA is involved in the water‐stress‐induced betaine accumulation in plant leaves. The present experiment, performed with the whole pear plant (Pyrus bretschneideri Redh. cv. Suli), revealed that the exogenously applied JA induced a significant increase of the betaine level in the pear leaves when the plants were not yet stressed by drought, and when the plants were subjected to water stress, the ‘JA plus drought’ treatment induced a significant higher betaine level than did the drought treatment alone. Meanwhile, the ‘JA plus drought’ treatment induced higher levels of betaine aldehyde dehydrogenase (BADH, E C 1.2.1.8) and activities in the leaves than did the drought treatment alone. These results obtained in the whole plant experiments were supported by the results of detached leaf experiments. In detached leaves JA induced significant increases in betaine levels, BADH activities and BADH protein amounts in a time‐ and concentration‐dependent manner. These data demonstrate that JA is involved in the drought‐induced betaine accumulation in pear leaves.     

Effect of salinity and abscisic acid on accumulation of glycinebetaine and betaine aldehyde dehydrogenase mRNA in Sorghum leaves (Sorghum bicolor)

The effects of salt stress and abscisic acid (ABA) on the expression of betaine aldehyde dehydrogenase (BADH) were determined in sorghum (Sorghum bicolor L.) plants. BADH mRNA expression was induced by salinity, and the timing coincided with the observed glycinebetaine (betaine) accumulation. The leaf water potential in the leaves of the sorghum plants was significantly affected by salinity. In response to salinity, betaine, ABA, Na and Cl accumulations increased 6-, 16-, 90-, and 3-fold, respectively. In the leaf disks from unsalinized plants incubated on NaCl, or ABA solution, the BADH mRNA level was lower than in the ABA-treated disks. Exogenous application of the ABA biosynthetic inhibitor fluridone to the NaCl-treated disks reduced the ABA accumulation and BADH mRNA levels compared with NaCl-treated leaves. The results indicate that the salt-induced accumulation of betaine and BADH mRNA coincides with the presence of ABA.     

盐胁迫下三色苋甜菜碱及有关酶含量的变化

三色苋(Amaranthus tricolor)不同器官中的甜菜碱(GB)含量显著不同.除子叶外,根、茎和叶的GB含量和茎、叶中的胆碱单加氧酶(CMO)含量都因300 mmol/L的NaCl处理而增加.甜菜碱醛脱氢酶(BADH)的表达无论盐处理与否在所有器官中都能检测到,其含量变化不大.当种子发芽时,具备合成GB的能力,CMO含量增加;在此之前未能检测到CMO,也不能合成GB.研究结果表明三色苋响应盐胁迫而合成GB的关键酶是CMO.     

Betaine aldehyde dehydrogenase in sorghum.

The ability to synthesize and accumulate glycine betaine is wide-spread among angiosperms and is thought to contribute to salt and drought tolerance. In plants glycine betaine is synthesized by the two-step oxidation of choline via the intermediate betaine aldehyde, catalyzed by choline monooxygenase and betaine aldehyde dehydrogenase (BADH). Two sorghum (Sorghum bicolor) cDNA clones, BADH1 and BADH15, putatively encoding betaine aldehyde dehydrogenase were isolated and characterized. BADH1 is a truncated cDNA of 1391 bp. BADH15 is a full-length cDNA clone, 1812 bp in length, predicted to encode a protein of 53.6 kD. The predicted amino acid sequences of BADH1 and BADH15 share significant homology with other plant BADHs. The effects of water deficit on BADH mRNA expression, leaf water relations, and glycine betaine accumulation were investigated in leaves of preflowering sorghum plants. BADH1 and BADH15 mRNA were both induced by water deficit and their expression coincided with the observed glycine betaine accumulation. During the course of 17 d, the leaf water potential in stressed sorghum plants reached -2.3 MPa. In response to water deficit, glycine betaine levels increased 26-fold and proline levels increased 108-fold. In severely stressed plants, proline accounted for > 60% of the total free amino acid pool. Accumulation of these compatible solutes significantly contributed to osmotic potential and allowed a maximal osmotic adjustment of 0.405 MPa.     

Salt-inducible betaine aldehyde dehydrogenase from sugar beet: cDNA cloning and expression

Members of the Chenopodiaceae, such as sugar beet and spinach, accumulate glycine betaine in response to salinity or drought stress. The last enzyme in the glycine betaine biosynthetic pathway is betaine aldehyde dehydrogenase (BADH). In sugar beet the activity of BADH was found to increase two- to four-fold in both leaves and roots as the NaCl level in the irrigation solution was raised from 0 to 500 mM. This increase in BADH activity was paralleled by an increase in level of translatable BADH mRNA. Several cDNAs encoding BADH were cloned from a gt10 libary representing poly(A)⁺ RNA from salinized leaves of sugar beet plants, by hybridization with a spinach BADH cDNA. Three nearly full-length cDNA clones were confirmed to encode BADH by their nucleotide and deduced amino acid sequence identity to spinach BADH; these clones showed minor nucleotide sequence differences consistent with their being of two different BADH alleles. The clones averaged 1.7 kb and contained an open reading frame predicting a polypeptide of 500 amino acids with 83% identity to spinach BADH. RNA gel blot analysis of total RNA showed that salinization to 500 mM NaCl increased BADH mRNA levels four-fold in leaves and three-fold in the taproot. DNA gel blot analyses indicated the presence of at least two copies of BADH in the haploid sugar beet genome.     

Abscisic acid is involved in the water stress-induced betaine accumulation in pear leaves

ABA exogenously applied to the leaves of the whole plants of pear (Pyrus bretschneideri Redh. cv. Suly grafted on Pyrus betulaefolia Rehd.) significantly increased the betaine concentrations in the leaves when the plants were well watered. The plants subjected to 'drought plus ABA' treatment had significantly higher betaine concentrations in their leaves than those given drought treatment alone. The 'drought plus ABA' treatment increased the amount of betaine aldehyde dehydrogenase (BADH, EC 1.2.1.8) and its activity in the leaves more than did the drought treatment alone. The experiments with detached leaves showed that ABA treatment significantly increased the concentration of betaine, activity of BADH and apparent amount of BADH in non-dehydrated leaves, and enhanced the accumulation of betaine, activity of BADH and apparent amount of BADH in dehydrated leaves. These effects of ABA were both time- and dose-dependent. Two ABA isomers, (-)-cis, trans-ABA and 2-trans, 4-trans-ABA, had no effect on the betaine accumulation in the leaves, showing that the ABA-induced effects are specific. These data demonstrate that ABA is involved in the drought-induced betaine accumulation in the pear leaves.     

Physiological and Growth Responses of Tomato Progenies Harboring the Betaine Alhyde Dehydrogenase Gene to Salt Stress

The responses of five transgenic tomato （Lycopersicon esculentum Mill） lines containing the betaine aldehyde dehydrogenase （BADH） gene to salt stress were evaluated. Proline, betaine （N, N, N-trimethylglycine, hereafter betalne）, chlorophyll and ion contents, BADH activity, electrolyte leakage （EL）, and some growth parameters of the plants under 1.0% and 1.5% NaCl treatments were examined. The transgenic tomatoes had enhanced BADH activity and betaine content, compared to the wild type under stress conditions. Salt stress reduced chlorophyll contents to s higher extent in the wild type than in the transgenic plants. The wild type exhibited significantly higher proline content than the transgenic plants at 0.9% and 1.3% NaCh Cell membrane of the wild type was severely damaged as determined by higher EL under salinity stress. K^＋ and Ca^2＋ contents of all tested lines decreased under salt stress, but the transgenic plants showed a significantly higher accumulation of K^＋ and Ca^2＋ than the wild type. In contrast, the wild type had significantly higher CI- and Na^2＋ contents than the transgenic plants under salt stress. Although yield reduction among various lines varied, the wild type had the highest yield reduction. Fruit quality of the transgenic plants was better in comparison with the wild type as shown by a low ratio of blossom end rot fruits. The results show that the transgenic plants have improved salt tolerance over the wild type.     

Seed germination of the halophyteSuaeda japonica under salt stress

Suaeda japonica Makino belonging to the family Chenopodiaceae, is a halophyte and grows at the shore of Ariake sea in Japan. This plant presumably possesses high salt resistant nature, thus, we examined the mechanisms of seed germination under salt stress. The seeds maintained 80% germination rates on the medium containing 0.7 M NaCl. Germination rates varied depending on salt type; the germination rates under NaCl or KCI exhibited relatively lower values than ones under sodium gluconate or potassium gluconate. This different responses for salts seemed to be as a result of the presence of Cl⁻ ions. Although very high levels of betaine (compatible solute), were kept in the seedlings grown under no salt stress, the contents gradually increased as concentration of NaCl increased. Betaine is a factor present in plants that works to alleviate the effects of excessive soil salts. It is synthesized in leaves from betaine aldehyde, and this process is catabolized by betaine aldehyde dehydrogenase (BADH). When the seedlings were cultivated on the medium without NaCl, relatively high level of BADH activity was found. The activity increased 5-fold in the seedlings grown under 0.5 M NaCl stress. Increases in betaine content and BADH activity were found during seed germination. InS. japonica, the salt stress promoted BADH activity, subsequently endogenous betaine contents were increased, and increased betaine seemed to secure seed germination under salt stress.     

Levels of Betaine and Betaine Aldehyde Dehydrogenase Activity in the Green Leaves, and Etiolated Leaves and Roots of Barley

The accumulation of betaine and the induction of betaine aldehydedehydrogenase, which catalyzes the last step in the synthesisof betaine, were analyzed in salt-stressed barley leaves. Whenhydroponically grown barley plants were transferred to a mediumthat contained 200 mM NaCl, the levels of both betaine and thetotal extractable betaine aldehyde dehydrogenase activity inthe leaves increased approximately 7-fold and 3-fold when calculatedon the basis of total leaf protein, respectively, over the courseof 7 days. Betaine aldehyde dehydrogenase activity was alsodetected in either etiolated leaves or roots of barley plantsgrown under aseptic conditions. Betaine was detected in bothetiolated leaves and roots at levels that were about 20% ofthat in green leaves when calculated on a fresh weight basis. ¹ This research was supported financially by a research grantfrom the Ministry of Education, Science and Culture (63560080) (Received March 9, 1990; Accepted May 29, 1990)     

Drought stress induced changes in some organic substances in nodules and other plant parts of two potential legumes differing in salt tolerance

A greenhouse experiment was conducted to assess the effect of water stress on growth and metabolic changes in nodules and other plant parts of two leguminous species, Phaseolus vulgaris and Sesbania aculeata, with the major objective that nodules play a vital role in drought tolerance. Imposition of water deficit conditions for 45 days to 15-day-old plants of P. vulgaris and S. aculeata reduced shoot mass and nodule mass of both species, but the reduction was more pronounced in P. vulgaris than in S. aculeata. Nitrate reductase (NR) activity was reduced more in the leaves and nodules of P. vulgaris than in S. aculeata. Soluble proteins in the nodules of S. aculeata were more decreased as compared to that in P. vulgaris. Free amino acids increased in all parts of both species due to water deficit, but a higher increase was observed in leaf and nodules of P. vulgaris than in S. aculeata. Osmoprotectants such as proline and glycine betaine increased more in the nodules and other parts of S. aculeata under drought stress. In conclusion, S. aculeata (salt tolerant) showed a higher degree of drought tolerance than P. vulgaris (salt sensitive). Drought tolerance of S. aculeata was found to be associated with a smaller reduction in number and mass of root nodules, a high activity of nitrate reductase in leaves and nodules, high accumulation of free proline in roots and nodules, and high glycine betaine content in nodules.     

外源甜菜碱对低温胁迫下香蕉内源甜菜碱合成的影响

以巴西香蕉(MusaAAA Giant Cavendish cv.Brazil)幼苗为试验材料,用不同浓度外源甜菜碱(BT)预处理香蕉幼苗后,置于人工气候箱中模拟低温(7℃)胁迫,分别测定香蕉叶片和根系内源甜菜碱的含量和甜菜碱合成关键酶甜菜碱醛脱氢酶(BADH)活性,以探讨外源甜菜碱对香蕉叶片和根系内源甜菜碱合成的影响.结果显示:7℃低温胁迫16 h后,10 mg/L外源甜菜碱即可极显著提高香蕉幼苗叶片BADH活性,叶片内源BT含量也同步极显著增加,低温胁迫24h后根系内源甜菜碱的含量虽显著高于常温对照,其BADH活性却无显著提升.同时,香蕉幼苗叶片内源BT含量的积累与叶片BADH活性的提高具有显著正相关关系,与根系内源BT含量的增加呈极显著正相关关系,与外源BT浓度无显著相关性.研究表明,外源甜菜碱可促进低温胁迫下香蕉内源甜菜碱的合成和积累,叶片和根系均具有合成内源BT的能力.     

Isolation of a choline monooxygenase cDNA clone from Amaranthus tricolor and its expressions under stress conditions

INTRODUCTIONAmaranth is a C4 dicotyledonous mesophytecrop plant. A. tricofor is a major variety for veg-etable and ornamental crops, and is widely culti-vated in the wor1d. Osmoprotectant glycine betaine(GB) was detected in Amaranthaceae, A. HyPochon-driacus L[2] and A. Caudatus L[3, 4]. GB iswidespread and an effective osmoprotectant in manyplants[3]. We studied the photosynthetic adaptationmechanism of A. trico1or under salt stress due to ac-cumulation of GB[5].GB is synthesized …     

Regulation of betaine synthesis by precursor supply and choline monooxygenase expression in Amaranthus tricolor

In plants, betaine is synthesized upon abiotic stress via choline oxidation, in which choline monooxygenase (CMO) is a key enzyme. Although it had been thought that betaine synthesis is well regulated to protect abiotic stress, it is shown here that an exogenous supply of precursors such as choline, serine, and glycine in the betaine-accumulating plant Amaranthus tricolor further enhances the accumulation of betaine under salt stress, but not under normal conditions. Addition of isonicotinic acid hydrazide, an inhibitor of glycine decarboxylase, inhibited the salinity-induced accumulation of betaine. Salt-induced accumulation of A. tricolor CMO (AmCMO) and betaine was much slower in roots than in leaves, and a transient accumulation of proline was observed in the roots. Antisense expression of AmCMO mRNA suppressed the salt-induced accumulation of AmCMO and betaine, but increased the level of choline approximately 2- 3-fold. This indicates that betaine synthesis is highly regulated by AmCMO expression. The genomic DNA, including the upstream region (1.6 kbp), of AmCMO was isolated. Deletion analysis of the AmCMO promoter region revealed that the 410 bp fragment upstream of the translation start codon contains the sequence responsive to salt stress. These data reveal that the promoter sequence of CMO, in addition to precursor supply, is important for the accumulation of betaine in the betaine-accumulating plant A. tricolor.     

Plastid-expressed betaine aldehyde dehydrogenase gene in carrot cultured cells, roots, and leaves confers enhanced salt tolerance

Salinity is one of the major factors that limits geographical distribution of plants and adversely affects crop productivity and quality. We report here high-level expression of betaine aldehyde dehydrogenase (BADH) in cultured cells, roots, and leaves of carrot (Daucus carota) via plastid genetic engineering. Homoplasmic transgenic plants exhibiting high levels of salt tolerance were regenerated from bombarded cell cultures via somatic embryogenesis. Transformation efficiency of carrot somatic embryos was very high, with one transgenic event per approximately seven bombarded plates under optimal conditions. In vitro transgenic carrot cells transformed with the badh transgene were visually green in color when compared to untransformed carrot cells, and this offered a visual selection for transgenic lines. BADH enzyme activity was enhanced 8-fold in transgenic carrot cell cultures, grew 7-fold more, and accumulated 50- to 54-fold more betaine (93-101 micromol g(-1) dry weight of beta-Ala betaine and Gly betaine) than untransformed cells grown in liquid medium containing 100 mm NaCl. Transgenic carrot plants expressing BADH grew in the presence of high concentrations of NaCl (up to 400 mm), the highest level of salt tolerance reported so far among genetically modified crop plants. BADH expression was 74.8% in non-green edible parts (carrots) containing chromoplasts, and 53% in proplastids of cultured cells when compared to chloroplasts (100%) in leaves. Demonstration of plastid transformation via somatic embryogenesis utilizing non-green tissues as recipients of foreign DNA for the first time overcomes two of the major obstacles in extending this technology to important crop plants.     

Enhanced drought and salinity tolerance in transgenic potato plants with a BADH gene from spinach

Drought and salinity are the most important abiotic stresses that affect the normal growth and development of plants. Glycine betaine is one of the most important osmolytes present in higher plants that enable them to cope with environmental stresses through osmotic adjustment. In this study, a betaine aldehyde dehydrogenase (BADH) gene from spinach under the control of the stress-induced promoter rd29A from Arabidopsis thaliana was introduced into potato cultivar Gannongshu 2 by the Agrobacterium tumefaciens system. Putative transgenic plants were confirmed by Southern blot analysis. Northern hybridization analysis demonstrated that expression of BADH gene was induced by drought and NaCl stress in the transgenic potato plants. The BADH activity in the transgenic potato plants was between 10.8 and 11.7 U. There was a negative relationship (y = −2.2083x + 43.329, r = 0.9495) between BADH activity and the relative electrical conductivity of the transgenic potato plant leaves. Plant height increased by 0.4–0.9 cm and fresh weight per plant increased by 17–29% for the transgenic potato plants under NaCl and polyethylene glycol stresses compared with the control potato plants. These results indicated that the ability of transgenic plants to tolerate drought and salt was increased when their BADH activity was increased.     

Accumulation of glycinebetaine during cold acclimation and freezing tolerance in leaves of winter and spring barley plants

A study was performed to examine whether or not betaine (glycinebetaine), a compatible solute, is accumulated in response to cold stress and is involved in mechanisms that protect plants from freezing injury. For this purpose, we used near-isogenic lines of barley, with each line differing only in a single gene for the spring type of growth habit; the various lines were produced by back-crosses to a recurrent cultivar of the winter type. The winter type of growth habit requires a low temperature for triggering of flower development (vernalization), whereas the spring type does not. Betaine was accumulated to five times the basal level over the course of 3 weeks at low temperature (5 °C) in the winter-type cultivar and in a spring-sh line having the sh gene for the spring-type growth habit, but the level was only doubled in the spring-Sh3 line, which carried the Sh₃ gene for the spring-type growth habit. Among near-isogenic lines of the same cultivar, the levels of betaine accumulated in leaves at low temperature were well correlated with the percentages (on a dry weight basis) of green leaves that survived freezing injury (-5 °C). This observation indicates the possibility, separate from the recognized role of betaine in the response to salinity and/or drought, that betaine accumulates in response to cold stress and that the accumulation of betaine during cold acclimation is associated to some extent with freezing tolerance in leaves of barley plants.