花色形成与花生长的调控

结合笔者的研究结果,对光、糖和GAs在花生长及花色形成中的作用和可能的调节机制进行了综述。光通过光受体介导的高辐照度反应(HIR)和光合作用调控花生长及花色素苷合成;糖作为碳源和渗透调节因子,影响花瓣细胞的生长及花色素苷积累,依赖己糖激酶的信号途径可能在糖的调控中起作用;GAs通过调节特异基因的转录间接地诱导花色素苷合成途径中结构基因的表达。     

环境因子调控植物花青素苷合成及呈色的机理

花青素苷（anthocyanin）是决定被子植物花、果实和种皮等颜色的重要色素之一。花青素苷的合成与积累过程往往与植物发育过程密切相关,由内外因子共同控制。环境因子通过诱导植物体内花青素苷合成途径相关基因的表达来调控花青素苷的呈色反应。该文追踪了国内外相关研究,认为光是影响花青素苷呈色的主要环境因子之一,光质和光强均能在一定程度上影响花青素苷的合成,其中光质起着更为关键的作用;低温能诱导花青素苷的积累,高温则会加速花青素苷的降解;不同的糖类物质均能影响花青素苷的合成,大部分结构基因和调节基因的表达均受糖调控。关于花发育与花青素苷呈色的关系、观赏植物花色对环境因子的响应以及花青素苷抵御逆境的机理尚待深入研究。因此,综合考察花发育与植物花青素苷合成及其呈色之间的关系,特别是光周期对花发育的影响导致花青素苷合成及呈色的机理是花色研究的一个重要课题。利用环境因子调控花色将会极大地提高花卉的观赏价值。     

环境因子调控植物花青素苷合成及呈色的机理

花青素苷(anthocyanin)是决定被子植物花、果实和种皮等颜色的重要色素之一。花青素苷的合成与积累过程往往与植物发育过程密切相关, 由内外因子共同控制。环境因子通过诱导植物体内花青素苷合成途径相关基因的表达来调控花青素苷的呈色反应。该文追踪了国内外相关研究, 认为光是影响花青素苷呈色的主要环境因子之一, 光质和光强均能在一定程度上影响花青素苷的合成, 其中光质起着更为关键的作用; 低温能诱导花青素苷的积累, 高温则会加速花青素苷的降解;不同的糖类物质均能影响花青素苷的合成, 大部分结构基因和调节基因的表达均受糖调控。关于花发育与花青素苷呈色的关系、观赏植物花色对环境因子的响应以及花青素苷抵御逆境的机理尚待深入研究。因此, 综合考察花发育与植物花青素苷合成及其呈色之间的关系, 特别是光周期对花发育的影响导致花青素苷合成及呈色的机理是花色研究的一个重要课题。利用环境因子调控花色将会极大地提高花卉的观赏价值。     

‘津田芜菁’花色素苷生物合成相关基因的表达

利用黑暗、日光、人工恒定光处理花色素苷合成依光型的‘津田芜菁’试材。通过紫外．可见分光光度计测定恒定光处理下‘津田芜菁’块根皮中花色素苷的含量,结果表明,花色素苷含量与光处理时间成正相关。用从消减文库中筛选的花色素苷生物合成基因片段制备探针,Northern杂交结果显示,在所处理的48h之内,光可以诱导‘津田芜菁’中PAL、DFR、CHS、F3H和ANS基因的表达,这些基因的表达量随着光处理时间的延长而增加,而MYB基因的表达量在黑暗与光下基本相同。     

植物花色素苷生物合成的转录调控

转录调节是植物花色素苷生物合成途径中调节其结构基因表达的重要环节之一。近十多年来,通过调节转录因子的表达激活或抑制有效地调控植物中花色素苷的合成成了众多植物学家研究的重点。现简要介绍了花色素苷的合成运输过程与液泡的沉积扣押、转录因子与调控及转录调节在遗传改良中的应用等方面的研究进展。     

花色素苷对拟南芥耐盐性的影响

为探讨花色素苷在盐胁迫中的防御作用及其机制,以模式植物拟南芥(Arabidopsis thaliana)花色素苷合成途径相关基因缺失突变体(DFR基因缺失突变体tt3,CHS基因缺失突变体tt4,CHS、DFR基因双缺失突变体tt3tt4)及其野生型(WT)为材料,采用叶绿素荧光和超氧阴离子(O_2·~–)组织定位等方法,分析了tt3,tt4,tt3tt4和WT对盐胁迫处理的生理响应。结果表明,盐胁迫下3种缺失突变体叶片花色素苷含量的增加显著低于野生型,与WT相比,叶绿素荧光参数Fv/Fm、Yield、ETR、q P和NPQ下降较快,膜渗漏率升高显著,叶片O_2·~–积累程度为tt3tt4tt3/tt4WT。这表明花色素苷在植物抵御盐胁迫过程中起着重要作用,它可能是作为渗透调节剂及抗氧化剂来增强植物的耐盐性。因此,花色素苷含量可以作为筛选耐盐作物的指标。     

蓝光和蔗糖对拟南芥花色素苷积累和CHS基因表达的影响

以在20μmol m^-2s^-1白光下生长13d的拟南芥(Arabidopsis thaliana,Landsbcrg生态型)幼苗为材料,采用测定叶片花色素苷含量和Northern blot方法,研究蓝光与蔗糖在诱导植物花色素苷积累及相关基因表达中的作用。结果表明：蓝光处理后,叶片花色素苷积累随光强和照光时间的延长而增加,突变体hy4叶片的花色素苷含量明显低于野生型(WT),说明隐花色素1(cry1)是蓝光诱导花色素苷积累的主要光受体：WT中苯基苯乙烯酮合酶基因(CHS)的表达受蓝光诱导,处理4h即有表达,8h达到最高,之后逐渐下降;蓝光不能诱导突变体hy4中CHS基因的表达,说明cry1介导蓝光诱导CHS基因的表达。培养基中不含蔗糖,削弱了蓝光诱导的拟南芥叶片花色素苷的积累,CHS基因表达也受到抑制。蔗糖不仅作为碳源参与蓝光诱导的花色素苷积累,还可能作为信号分子参与蓝光诱导的CHS表达。     

植物花青苷代谢调控机理研究进展

花青苷是植物特有的黄酮类天然色素,具有较高的科研价值,是人们了解植物生命活动的一个重要途径。现有的研究表明,植物花青苷具有光保护、生物保护、有助花的传粉等生物学功能;通过多年努力,花青苷在植物体内合成的化学水平和分子水平的合成代谢途径已经找到,而花青苷在植物体内降解代谢途径研究也有了较大的进展。本文主要综述了近年来花青苷合成及降解途径机理研究进展,并对今后研究发展提出探讨和分析。     

桃树体不同部位果实着色差异及其与环境因子的关系研究

为探讨树体冠层不同部位桃果实着色机制差异及其与环境因子的关系,以晚熟桃品种‘霞晖8号’为试材,研究了果实3个典型发育时期(硬核期、膨大期、成熟期)树体冠层上部、中部外围、中部内膛和下部的温度、光照环境因子变化动态,并就其对果皮色泽、色素含量的影响及与果实着色相关的基因表达特点进行解析。结果表明:(1)与冠层下部果实相比,‘霞晖8号’冠层上部、中部外围和中部内膛成熟果实果皮a~*/b~*(红色饱和度/黄色饱和度)显著较高。(2)冠层下部成熟果实的果皮花色素苷含量最低而叶绿素含量最高,且与其他部位间差异显著。(3)果实不同发育时期花色素苷合成相关基因的表达量差异表明,果皮花色素苷合成是多基因协同调控的过程。(4)果实转色前,低光照强度抑制了花色素苷合成相关基因的表达,其中对UFGT、DFR、CHS基因的调控作用最明显;果实成熟期,与高光照条件相比,低光照条件下果皮花色素苷合成相关基因上调表达。研究认为,树体冠层不同部位光照条件差异可能是导致果实着色差异的主要环境因素之一,它通过调节与果皮花色素苷积累相关的基因表达水平控制果皮的着色。     

外源脱落酸对桃果实着色及相关基因表达的影响

以‘美香’桃为试验材料,于果实着色前用1 000、500、300mg/L的脱落酸(ABA)溶液处理果实,研究了ABA处理促进桃果皮着色的效果以及对果皮花色素苷合成相关基因表达的影响。结果表明:ABA处理显著提高了成熟果实可溶性固形物含量和果皮花色素苷含量;明显改善了果实着色,且以1 000mg/L效果最为明显。ABA处理显著促进了查尔酮合成酶基因(CHS)和二氢黄酮醇4-还原酶基因(DFR)的前期转录水平,同时促进了类黄酮葡萄糖苷转移酶基因(UFGT)和花色素合成酶基因(LDOX)表达高峰的前移。据此推测ABA可能参与了桃果实花色素苷合成的调控,对花色素苷合成具有促进作用。     

Identification of a major gene and RAPD markers for yellow seed coat colour in Brassica napus.

The development of yellow-seeded Brassica napus for improving the canola-meal quality characteristics of lower fibre content and higher protein content has been restricted because no yellow-seeded forms of B. napus exist, and their conventional development requires interspecific introgression of yellow seed coat colour genes from related species. A doubled-haploid (DH) population derived from the F1 generation of the cross 'Apollo' (black-seeded) x YN90-1016 (yellow-seeded) B. napus was analysed via bulked segregant analysis to identify molecular markers associated with the yellow-seed trait in B. napus for future implementation in marker-assisted breeding. A single major gene (pigment 1) flanked by eight RAPD markers was identified co-segregating with the yellow seed coat colour trait in the population. This gene explained over 72% of the phenotypic variation in seed coat colour. Further analysis of the yellow-seeded portion of this DH population revealed two additional genes favouring 'Apollo' alleles, explaining 11 and 8.5%, respectively, of the yellow seed coat colour variation. The data suggested that there is a dominant, epistatic interaction between the pigment I locus and the two additional genes. The potential of the markers to be implemented in plant breeding for the yellow-seed trait in B. napus is discussed.     

Histological Study of Seed Coat Development in Arabidopsis thaliana

Arabidopsis seed coat development using light and transmission electron microscopy revealed major morphological changes associated with the transition of the integuments into the mature seed coat. By the use of a metachromatic staining procedure, cytological events such as the production of phenolic compounds and acidic polysaccharides were followed. Immediately after fertilization, the cells of the inner epidermis of the inner integument became vacuolated and subsequently accumulated pigment within them. This pigment started to disappear from the cytoplasm at the torpedo stage of the embryo, as it became green. During the torpedo stage, mucilage began to accumulate in the cells of the external epidermis of the outer integument. Furthermore, starch grains accumulated against the central part of the inner periclinal wall of these cells, resulting in the formation of small pyramidal domes that persisted until seed maturity. At the maturation stage, when the embryo became dormant and colourless, a new pigment accumulation was observed in an amorphous layer derived from remnants of crushed integument layers. This second pigment layer was responsible for the brown seed colour. These results show that seed coat formation may proceed in a coordinated way with the developmental phases of embryogenesis. Received 25 May 1999/ Accepted in revised form 10 February 2000     

Violaxanthin,the major carotenoid pigment in Zea mays root cap during seed germination

Violaxanthin (5,6,5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene-3,3′-diol) was shown to be the major carotenoid in maize root cap during seed germination according to chromatographic and spectroscopic studies. The biosynthesis of this pigment is not influenced by light and the biological significance of this carotenoid in maize root tip is briefly discussed.     

Histolocalisation of the oil and pigments in the pumpkin seed

Pumpkin seed oil has a distinct taste and a characteristic green‐red colour. A green layer (chlorenchyma) can be observed in the cross section of the seed on the inner side of the testa. This layer is considered to be a source of protochlorophyll pigment that gives colour to the pumpkin seed oil. However, the histolocalisation of the pigment by selective method was not yet studied. In this study, we localised the oil to the small lipid droplets in the cotyledon cells by Rhodamine 6G lipophilic stain. Furthermore, we localised protochlorophyll to chlorenchyma by microscopic fluorimetry. Emission maximum of protochlorophyll was 700 nm when measured in the seed, but it shifted to 630 and 655 nm (two peaks) when measured in pumpkin seed oil or in the extract.     

Sn, a Light-Dependent and Tissue-Specific Gene of Maize: The Genetic Basis of Its Instability

The genetic system under investigation is defined by three major components: a gene, Sn, conferring tissue specific anthocyanin accumulation in different plant regions, light, required for color development in competent tissues, and another gene, Pl, substituting for light in its capacity to elicit pigment production. Attention is given in this paper to an Sn allele, symbolized Sn:bol3, capable of some constitutive pigmentation in seedlings and seed integuments. Sn:bol3 confers a higher pigment potential than the other alleles and is unstable. Its instability relates to its frequent changes from an original condition, indicated as Sn-s, to Sn-w, where -s and -w stand for strong and weak and refer to the two levels of seedling pigmentation. Weak derivatives arise spontaneously at a high frequency in homo- and heterozygous Sn:bol3 genotypes. In the latter, weak derivatives are also recovered on the chromosome originally devoid of Sn as if the heterozygous association had promoted "contamination" of one chromosome (recipient) with Sn coming from the other (donor). If the two chromosomes in the heterozygote are marked with contrasting alleles of R, a gene lying about two crossover units proximal to Sn, it appears that the R constitution of the recipient chromosome affects their constitution. Presence of R-r in fact leads to changes of both chromosomes in terms of Sn constitution, resulting in a majority of nonparental chromosomes, R-r Sn and r Sn-w or r sn, while replacement of R-r with R-g, a mutant derivative of R-r, leads to a drastic reduction in the yield of nonparental chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selection of the seeding media and the age and quantity of mycelia providing simultaneous biosynthesis of an antibiotic and pigment by the fungus Hypomyces rosellus

The authors observed maximum simultaneous biosynthesis of antibiotic and pigment in the microphilic fungus with using 48-hour seed mycelium having the specific growth rate of 0.008-0.011 h-1 in an amount of 5-7 per cent (v). The Balling 4 degrees wart and Chapek medium with 1 per cent of soybean flower and 1 per cent of corn steep liquor may be used for growing the seed mycelium. No significant effect of the seed medium composition and seed mycelium age on the pigment production was observed.     

A cytoplasmically inherited mutant controlling early chloroplast development in barley seedlings

Cytoplasmic line 2 (CL2) has been previously reported as a cytoplasmically inherited chlorophyll-deficient mutant selected from a chloroplast-mutator genotype of barley. It was characterized by a localized effect on the upper part of the first-leaf blade. At emergence the CL2 seedlings-phenotype varied from a grainy light green to an albino color. They gradually greened during the following days, starting from the base of the blade and extending to cover most of its surface when it was fully grown. The present results, from both light microscopy and transmission electron microscopy (TEM), confirmed the previously described positional and time-dependent expression of the CL2 syndrome along the first-leaf blade. During the first days after emergence, light microscopy showed a normally developed chloroplast at the middle part of the CL2 first-leaf blade, meanwhile at the tip only small plastids were observed. TEM showed that the shapes and the internal structure of the small plastids were abnormal, presenting features of proplastids, amyloplasts and/or senescent gerontoplasts. Besides, they lack plastid ribosomes, contrasting with what was observed inside chloroplasts from normal tips, which presented abundant ribosomes. Phenotypic observations and spectrophotometric analysis of seedlings produced by mother plants that had been grown under different temperatures indicated that higher temperatures during seed formation were negatively associated with pigment content in CL2 seedlings. In contrast, higher temperatures during the growth of CL2 seedlings have been associated with increased pigment content. Aqueous solution with kanamycin and streptomycin, which are antibiotics known to interfere with plastid gene translation, were used for imbibition of wild-type and CL2 seeds. Antibiotic treatments differentially reduced the chlorophyll content in the upper part of the first-leaf blade in CL2, but not in wild-type seedlings. These results suggest that in the wild-type, plastid-gene proteins which are necessary for chloroplast development and chlorophyll synthesis in the upper part of the first-leaf blade are usually synthesized during embryogenesis. However, under certain circumstances, in CL2 seedlings, they would be synthesized after germination. In addition, a shortening of the sheath has been observed in association with pigment decrease suggesting the existence of plastid factors affecting the expression of some nuclear genes. We consider the CL2 mutant a unique experimental material useful to study biological phenomena and external factors regulating plastid, and nuclear gene expression during embryogenesis and early seedling development.Communicated by R. Hagemann