太谷核不育小麦可育花药内游离脯氨酸的来源、利用及与不育花药败育的关系

太谷核不育小麦营养体内的游离脯氨酸能迅速地运入并积累于花药中,花药有将谷氨酸转化成脯氨酸的能力。脯氨酸向花药内以主动运输为主,能被DNP所抑制,与旗叶的功能密切相关。在发育阶段Ⅰ(小孢子释放前后),脯氨酸已不能由营养体运入不育花药,运输的障碍在花丝或花药中,不育花药缺乏游离脯氨酸可能是主要原因。发育阶段Ⅰ的可育花药内,脯氨酸是合成蛋白质或其他大分子物质的原料。因而,脯氨酸的缺乏可能是加速不育花药小孢子败育和小孢子释放后急剧解体的重要原因。     

盐胁迫下小麦苗叶片吡咯-5-羧酸还原酶活性和游离脯氨酸积累

受NaCl、KCl或MsCl_2胁迫的小麦幼苗,当外部溶液的渗透势由—160 kPa下降到—900 kPa时,叶片吡咯—5—羧酸还原酶(PSC)活性增高;渗透势由—900 kPa降低到—1500kPa,酶活性下降;胁迫 1d和 2d的幼苗,还原酶活性显著增加;3～6d酶活性无大变化。游离脯氨酸含量随溶液渗透势下降和培养时间的延长而提高。胁迫解除后酶活性和脯氨酸含量均降低。受NcCl胁迫义在ABA影响下的幼苗,P5C还原酶活性和脯氨酸含量高于仅受NaCl胁迫的幼苗。     

Proline biosynthesis in a proline-accumulating barley mutant

A barley (Hordeum vulgare L.) mutant, R5201, selected for resistance to 4? mM trans-4-hydroxyproline had a 3–6 fold increase in the soluble proline content of the leaf compared with the parent cultivar, Maris Mink. The mutant converted more [U-⁴C]glutamic acid to free proline in the leaves than Maris Mink but incorporation into protein proline was similar. Incorporation of radioactivity into proline was inhibited by exogenous proline more in Maris Mink than R5201, suggesting that feedback inhibition of proline biosynthesis is relaxed, but not absent in the mutant. When [1-¹⁴C]ornithine was the precursor, both R5201 and Maris Mink incorporated similar small amounts of label into soluble and protein proline. More protein proline was formed by both genotypes from labelled glutamic acid than from labelled ornithine. There may exist two routes of proline formation, where the glutamate pathway is synthetic and the ornithine pathway is catabolic.     

Proline involvement in the common sage antioxidant system in the presence of NaCl and paraquat

To elucidate proline antioxidant properties in common sage (Salvia officinalis L.) plants, they were treated with paraquat (a producer of superoxide radical) and/or NaCl and also with paraquat and proline at the stage of 4–5 true leaves. The paraquat solution (1 ml containing 0.1 μmol of the agent) was applied to the leaf surface; NaCl (200 mM) and proline (the final concentration of 5 mM) were added to nutrient medium. Experimental plants were firstly kept in darkness for 12 h, then illuminated, and in 3, 6, and 12 h, leaves and roots were fixed for biochemical analyses. The results obtained are in agreement with the supposition of proline antioxidant properties. In particular, it was established that paraquat induced a slight increase in the proline level in the leaves during dark period of plant growth and also during subsequent 3 h after light switching on. This transient proline accumulation in the leaves was accompanied by its level decrease in the roots. Proline addition to the nutrient medium of paraquat-treated plants neutralized paraquat damaging action on the leaves. In the presence of paraquat, proline treatment reduced the accumulation in the roots of hydrogen peroxide and malondialdehyde, the product of membrane lipid peroxidation. It also affected indirectly the activities of superoxide dismutase (SOD) and free, covalently bound, and ionically bound peroxidases. Keeping in mind that, in the presence of paraquat, superoxide-induced changes in SOD activity in the roots were negatively correlated with the level of proline, which content was the highest during the last hours of experiments, we can conclude that proline antioxidant effects are manifested only after 12 h of stressor action, whereas antioxidant enzymes are involved in ROS scavenging during the earlier stage of damaging factor action.     

Fasciolicidal potential of proline analogues and proline biosynthesis inhibitors

Sheers Marion, Campbell Anne J., Beames D. J., Edwards S. R., Moore R. J. and Montague P. E. 1982. Fasciolicidal potential of proline analogues and proline biosynthesis inhibitors. International Journal for Parasitology12: 47–52. Hydroxylamine HCl and thiazolidine-4'-carboxylic acid, known inhibitors of important enzymes of proline biosynthesis, inhibited to a similar extent the arginine-dependent proline production by the liver fluke Fasciola hepofica; in vitro there appeared to be no correlation between inhibition of proline synthesis and deterioration of the fluke. Another known inhibitor, thiosemicarbazide, had no effect on arginine-dependent proline production in vitro. None of these compounds was effective in vivo either as a flukicidal agent per se or in the prevention of the establishment of fluke in the bile duct of rats. A variety of proline analogues was also tested for flukicidal activity in vitro and in vivo as well as for their ability to inhibit the establishment of fluke in the bile duct of rats. Only one was effective in vitro and none was effective in vivo. Also continuous administration of l-azetidine-2-carboxylic acid failed to prevent the establishment of an infection of liver fluke in the bile duct. It is concluded that there is little prospect of a successful approach to chemotherapy of fascioliasis in this area.     

Water stress-induced alterations in the proline metabolism of drought-susceptible and -tolerant cassava (Manihot esculenta) cultivars

The free proline levels and activities of ornithine aminotransferase (EC 2.6.1.13) and proline oxidase (EC 1.5.2.2), two of the enzymes involved in proline metabolism were studied during the induction of water stress in a drought susceptible (M-4) and a drought tolerant (S-1315) cultivar of cassava ( Manihot esculenta Crantz). Water stress induced by polyethylene glycol (MW 6000, osmotic potential — 1.65 MPa) caused a ca 25-fold increase in proline in young excised leaves of the susceptible cultivar (M-4) while the increase was about 9-fold in the tolerant cultivar (S-1315). The activity of ornithine aminotransferase (OAT), a key enzyme involved in the biosynthesis of proline, was found to increase 3-fold in water stressed leaves of M-4 and about 2-fold in those of S-1315. The activity of proline oxidase, which is involved in the degradation of proline to pyrroline-5-carboxylate, was reduced by 50% in M-4 and nearly 25% in S-1315 on water stress. Comparison of the kinetic properties of OAT showed that the enzyme from water-stressed leaves is more stable to heat inactivation compared to that of control. These results indicate that during water stress there are alterations in the metabolism of proline in cassava, and the extent of alteration varies between drought-susceptible and -tolerant cultivars.     

环己亚胺对盐诱导游离脯氨酸累积的影响

环己亚胺(CHX)单独作用会增加高梁苗中游离脯氨酸的含量,原因可能有:一是CHX抑制了根的正常吸收功能,导致植株失水,游离脯氨酸增加;二是CHX抑制了蛋白质合成,使总的游离氨基酸累积,从而也表现出游离脯氨酸含量的增加,后者可能更为主要。为此,用CHX研究与脯氨酸合成有关的基因活性化或表达时,一定要考虑CHX单独的作用。NaCl诱导的游离脯氨酸的累积可被CHX处理所抑制。在NaCl处理2～4h内加CHX后,抑制效果几乎可达到100％,以后随CHX处理的时间越长,其抑制作用越小。     

Free proline levels in ulva (chlorophyta) in response to hypersalinity: elevated nacl in seawater versus concentrated seawater (Note)

Changes in free proline concentrations following exposure to elevated NaCl in 35 psu artificial seawater (ASW) (an imbalance in ion ratio) or concentrated ASW (constant ion ratio) were investigated in the intertidal green alga Ulva fasciata Delile. When exposed to 55 psu achieved by adding NaCl to 35 psu ASW, free proline concentrations increased at hour 3 and reached a plateau after 12 h, whereas free proline concentrations in response to 55 psu achieved by concentrating ASW were constant during the treatment period. It is likely that an imbalance in ion ratio is a cue for the induction of a moderate accumulation of free proline in U. fasciata .     

Effect of water stress on the enzymes of nitrate metabolism in two Brassica species

Brassica juncea (drought susceptible) and B. campestris (drought tolerant) were germinated under simulated water stress created by polyethylene glycol (MW 6000). The two species showed characteristic differences in dry weight, nitrate reductase, aspartate amino transferase, alanine aminotransferase, glutamate dehydrogenase and free proline accumulation in the embryo axis under water stress. Stress resulted in the decreased activities of these enzymes and the decrease was more in B. juncea than in B. campestris. In both species, protein content was higher under stress. In B. juncea, a 12-fold increase in free proline occurred as compared to a 7-fold increase in B. campestris at ?6 atm osmotic potential.     

NaCl对小麦苗叶片脯氨酸氧化酶活性和游离脯氨酸累积的影响

在含NaCl营养液中培养的小麦幼苗较之无NaCl营养液中的幼苗。其脯氨酸氧化酶活性降低,而游离脯氨酸含量则升高;培养液的渗透势越低,培养时间越长,则脯氨酸氧化酶的活性越低,且游离脯氨酸的含量越高。去除胁迫后酶活性恢复,脯氯酸含量下降。不同渗透剂对氧化酶活性抑制强弱顺序为MgCl_2>NaCl>甘露醇,引起脯氨酸累积效应的强度顺序为MgCl_2>NaCl>甘露醇。超微结构显示,高NaCl浓度下部分线粒体结构受损伤,膜和嵴部分消失。     

Prolindehydrogenase aus keimenden farnsporen

A soluble enzyme which converts proline to glutamic acid using NAD as coenzyme was isolated from young prothallia and spores of the fern Anemia phyllitidis. The purification was about 36-fold. The pH optimum is between 10·2 and 10·7; the K_m for proline is 4·6 × 10⁻⁴ M and for NAD 3·4 × 10⁻⁴ M. There are no multiple forms of this enzyme, as proved by gel electrophoresis.     

山黧豆幼苗对干旱胁迫的生理响应

用PEG6000模拟干旱对山黧豆进行胁迫。结果发现,胁迫初期（0~48 h）,突然的水分亏缺使气孔导度（Sc）和蒸腾速率（Tr）迅速下降,而净光合速率（Pn）和水分有效利用率（WUE）基本维持稳定。胁迫后期（48~108 h）,上述四个光合指标均不同程度地向对照水平恢复;脯氨酸和相对电导率（REC）受胁迫强度影响较小,但与胁迫时间呈明显正相关,分别在48和60 h增幅最大,而且当REC上升至对照的50%左右时,脯氨酸含量已达对照的14倍之多。由此认为,山黧豆可能主要通过迅速减小Sc和Tr以及大量而急剧的积累脯氨酸来减轻干旱所造成的伤害。     

Genetic control of susceptibility to hydroxyproline in Drosophila.

Hydroxyproline (OHP) is known to produce morphological abnormalities in susceptible Drosophila. In some, OHP prevents head eversion during pupation producing a cryptocephal (crc) phenocopy, others fail to fully stretch legs and wings producing a shortened distance between these appendages (LWD). In this paper the genetic basis of susceptibility to OHP is explored and compared to the control of susceptibility to glucosamine (GA) which also produces a crc phenocopy. The data suggest that genes providing resistance to the effects of GA are different from those conferring resistance to OHP. Furthermore, genes providing resistance to the crc effects of OHP appear to be different from those controlling resistance-to the LWD effects. Intrastrain gene coadaptation also seems to be important in resistance to OHP. The relevance of these results to the problem of the genetic control of developmental buffering is briefly discussed.     

Genetic analysis of Pycr1 and Pycr2 in mice

The final step in proline biosynthesis is catalyzed by three pyrroline-5-carboxylate reductases, PYCR1, PYCR2, and PYCR3, which convert pyrroline-5-carboxylate (P5C) to proline. Mutations in human PYCR1 and ALDH18A1 (P5C Synthetase) cause Cutis Laxa (CL), whereas mutations in PYCR2 cause hypomyelinating leukodystrophy 10 (HLD10). Here, we investigated the genetics of Pycr1 and Pycr2 in mice. A null allele of Pycr1 did not show integument or CL-related phenotypes. We also studied a novel chemically-induced mutation in Pycr2. Mice with recessive loss-of-function mutations in Pycr2 showed phenotypes consistent with neurological and neuromuscular disorders, including weight loss, kyphosis, and hind-limb clasping. The peripheral nervous system was largely unaffected, with only mild axonal atrophy in peripheral nerves. A severe loss of subcutaneous fat in Pycr2 mutant mice is reminiscent of a CL-like phenotype, but primary features such as elastin abnormalities were not observed. Aged Pycr2 mutant mice had reduced white blood cell counts and altered lipid metabolism, suggesting a generalized metabolic disorder. PYCR1 and -2 have similar enzymatic and cellular activities, and consistent with previous studies, both were localized in the mitochondria in fibroblasts. Both PYCR1 and -2 were able to complement the loss of Pro3, the yeast enzyme that converts P5C to proline, confirming their activity as P5C reductases. In mice, Pycr1; Pycr2 double mutants were sub-viable and unhealthy compared to either single mutant, indicating the genes are largely functionally redundant. Proline levels were not reduced, and precursors were not increased in serum from Pycr2 mutant mice or in lysates from skin fibroblast cultures, but placing Pycr2 mutant mice on a proline-free diet worsened the phenotype. Thus, Pycr1 and -2 have redundant functions in proline biosynthesis, and their loss makes proline a semi-essential amino acid. These findings have implications for understanding the genetics of CL and HLD10, and for modeling these disorders in mice.     

Sources of proline-nitrogen in water-stressed soybean (Glycine max). II. Fate of 15N-labelled protein

The absorption of nitrate, protein metabolism and the source of nitrogen for proline synthesis were studied in soybean ( Glycine max L. cv. Akisengoku) with ¹⁵N tracer technique under water stress conditions. The absorption of nitrate was sensitive to water stress and the flow of nitrate into the leaves completely ceased under severe stress conditions. Net protein loss from the water-stressed leaves was attributable to both a decrease in synthetic activity and a stimulation of protein degradation. Proline and asparagine accumulated extensively in the severely water-stressed plant tissues, especially in the younger green leaves. Fifty four % of the loss of leaf protein-¹⁵N during the stress period was balanced by a gain in ¹⁵N in the free amino acids, 41% being found in proline and asparagine. The increase in ¹⁵N content of the free proline was 3 times greater than the decrease in ¹⁵N content of the protein-bound proline in the leaf. The results indicate that the accumulation of proline in response to water stress was caused by enhanced synthesis and that the nitrogen source for this proline is the leaf protein. The possible association of these findings with stress tolerance is discussed.     

干旱胁迫对苜蓿脯氨酸累积的影响

用PEG-6000高渗溶液模拟干旱胁迫,研究了干旱胁迫对首蓿累积脯氨酸的影响,实验结果表明,四种苜蓿在不同浓度PEG溶液和一定时间范围内都有游离脯氨酸的累积,而且每种苜蓿在20%PEG溶液中48h游离脯氨酸的量最多,以中牧1号苜蓿累积量最高,累积脯氨酸是苜蓿幼苗对干旱环境的适应性表现。     

Stress‐driven increase in proline levels,and not proline levels themselves,correlates with the ability to withstand excess salt in a group of 17 Italian rice genotypes

• In most plant species, a rapid increase in free proline content occurs following exposure to hyperosmotic stress conditions. However, inconsistent results were reported concerning the role of such an increase on the plant response to water shortage or excess salt. Therefore, the possibility that proline accumulation may help the cell to withstand stress conditions, or that it simply represents a stress marker, is still a matter of debate. A possible relationship between proline accumulation and salt tolerance was investigated in a set of 17 Italian rice varieties.
• Rice seedlings were exposed to increasing salt concentrations during germination and early growth. The resulting levels of free proline were measured separately in shoots and roots and compared to those in untreated controls. Results were related to the corresponding ability of a given genotype to tolerate stress conditions.
• Neither absolute proline levels in untreated or in salt‐stressed seedlings showed a straightforward relationship to the relative tolerance to salt, estimated as conductivity values able to reduce growth by 10 or 50%. Conversely, a highly significant correlation was found between the increase in proline levels in shoots and the ability to withstand stress.
• The results strengthen a recent hypothesis suggesting than an increase in proline metabolic rates, more than the resulting proline content, may help the cell to counteract the effects of abiotic stress conditions.

     

外源H2O2处理对唐古特白刺愈伤组织脯氨酸代谢的影响

以唐古特白刺（Nitraria tangutorum Bobr.）愈伤组织为材料,研究外源H₂O₂（2和10 μmol·L^-1）处理下其脯氨酸含量及相关代谢酶活性的变化,试图从细胞水平揭示H₂O₂影响脯氨酸代谢的生理机制。结果显示,2和10 μmol·L^-1 H₂O₂处理24 h使唐古特白刺愈伤组织脯氨酸含量分别变为对照的112%和92%,而处理72 h后,脯氨酸含量增加为对照的141%和119%;与对照相比,外源H₂O₂处理诱导愈伤组织脯氨酸脱氢酶活性降低,而谷氨酸激酶活性升高,但鸟氨酸转氨酶活性无显著变化;此外,H₂O₂处理使唐古特白刺愈伤组织内源性H₂O₂含量升高。结果表明,外源H₂O₂诱导了唐古特白刺愈伤组织H₂O₂含量的增高和脯氨酸的积累,且H₂O₂处理下脯氨酸脱氢酶活性的降低及谷氨酸激酶的升高与愈伤组织脯氨酸的积累有关。     

Free proline accumulation in maize (Zea mays L.) subjected to prolonged waterlogging

Summary Free proline accumulation was measured in two maize genotypes (Ganga-2 and D747) subjected to waterlogging for three weeks at the knee high stage. The initial content of free proline was same in both the genotypes (0.1 micromole per gram fresh weight of leaves). The free proline content increased in both the genotypes when the plants were subjected to waterlogging. However, Ganga-2 accumulated more free proline than D747. Ganga-2 appeared to be more waterlogging tolerant than D-747.