植物春化特性及春化作用机理

春化作用是某些高等植物成花转变的重要环节,被认为是植物在低温诱导下促使其相关基因的表达,从而导致生理状态转变的一种受遗传控制的生理过程。本文对植物春化反应特性、春化作用的生理生化特性及春化作用的分子生物学等方面的研究进展进行了概述,并对春化研究中的问题进行了分析和展望。     

植物春化作用的分子机制及应用

植物能响应环境中的低温信号实现开花调控，这种经历低温促使植物开花的作用即为春化作用。本文结合国内外春化作用的研究进展，概述春化作用的发现和特点，阐述模式植物拟南芥及单子叶作物的春化作用分子机制，并举例说明春化作用在农业、园艺等方面的应用。     

高等植物春化作用研究进展

环境因子(低温诱导或称春化作用)在高等植物的生长发育调控中起着重要作用。本文就近年来春化作用诱导的开花启动研究领域中的进展从春化过程中的多步骤性、成花决定过程控制的多途径性、接受春化刺激的位置与分化启动的关系、以及春化作用的分子机理等几个方面进行了简要综述。并对春化相关基因克隆方面的进展进行了分析和综述。     

高等植物春化作用研究进展

环境因子（ 低温诱导或称春化作用） 在高等植物的生长发育调控中起着重要作用。本文就近年来春化作用诱导的开花启动研究领域中的进展从春化过程中的多步骤性、成花决定过程控制的多途径性、接受春化刺激的位置与分化启动的关系、以及春化作用的分子机理等几个方面进行了简要综述。并对春化相关基因克隆方面的进展进行了分析和综述     

小麦春化发育的分子调控机理研究进展

春化发育特性是小麦品种的重要性状,直接影响着小麦品种的种植范围和利用效率.本文就小麦春化相关基因的发现,以及对春化相关基因VRN1、VRN2和VRN3的克隆、表达特性以及春化发育分子调控机理方面的研究进展进行了综述.     

与拟南芥春化作用相关的基因及其春化记忆模型

植物能感应春化并记住这一效应,且通过一系列的信号传导,最终调控开花。文章就拟南芥的春化相关的基因,春化记忆分子模型、春化记忆与开花调控途径以及与此不同的另一种春化记忆模型和小麦春化记忆分子机制的研究进展作了介绍。     

植物春化用的分子机理

春化作用在控制高等植物开花中起着重要的作用。本文综述了近年来以拟南芥(Arabidopsis thaliana)和冬小麦(Triticum aestivum)为主要研究对象进行的有关春化作用分子机制的研究; 概括和分析了已经分离得到的与春化有关的基因的功能及其调控方式以及各基因间的相互作用。     

植物春化作用的分子机理

春化作用在控制高等植物开花中起着重要的作用。本文综述了近年来以拟南芥（Arabidopsis thaliana）和冬小麦（Triticum aestivum）为主要研究对象进行的有关春化作用分子机制的研究;概括和分析了已经分离得到的与春化有关的基因的功能及其调控方式以及各基因间的相互作用。     

冬小麦春化相关基因cDNA(verc203)片段序列的分析

春化作用是高等植物发育的重要环节之一,它是受遗传控制的生理过程,人们对此现象已作了生态、生理和生化方面的研究（谭克辉1983）。认为植物茎尖生长点接受低温诱导后,会引起体内许多代谢途径和方式的顺序改变（种康和谭克辉1993）,可能导致春化相关基因启动表达。有人（Burn等1993）提出春化相关基因启动表达可能是基因脱甲基化结果的观点。但这一假说尚缺乏直接的强有力证据。违斌和谭克辉（199）系统地研究了冬小麦春化过程中核酸、蛋白质代谢与春化作用的直接相关关系和春化特异蛋白质代谢与特异性rnRNA出现的重要意义,确信春化…     

红菜薹春化相关基因的克隆与表达

红菜薹是一种不经春化处理就可开花的天然早花突变体.根据已报道的拟南芥和芸薹属植物春化相关基因的保守区域设计引物,通过PCR和RT-PCR方法从红菜薹中克隆得到了4个春化相关的关键基因片段:BrFRI、BrFLC、BrVIN3、BrSOC1,获得BrFRI起始密码子附近的关键序列,其中BrVIN3基因序列为首次报道,含有PHD区关键区域.Northern和半定量RT-PCR表达分析表明:BrFRI的表达不受春化作用的影响,BrFLC受春化作用的抑制,BrVIN3和BrSOC1受春化作用的诱导.     

Vernalization sensitivity in Arabidopsis thaliana (Brassicaceae): the effects of latitude and FLC variation

Latitudinal variation in climate is predicted to select for latitudinal differentiation in sensitivity to the environmental cues that signal plants to flower at the appropriate time for a given climate. In Arabidopsis thaliana, flowering is promoted by exposure to cold temperatures (vernalization), and several vernalization pathway loci are known. To test whether natural variation in vernalization sensitivity could account for a previously observed latitudinal cline in flowering time in A. thaliana, we exposed 21 European accessions to 0, 10, 20, or 30 d of vernalization and observed leaf number at flowering under short days in a growth chamber. We observed a significant latitudinal cline in vernalization sensitivity: southern accessions were more sensitive to vernalization than northern accessions. In addition, accessions that were late flowering in the absence of vernalization were more sensitive to vernalization cues. Allelic variation at the flowering time regulatory gene FLC was not associated with mean vernalization sensitivity, but one allele class exhibited greater variance in vernalization sensitivity.     

Thermoinduction of genes encoding the enzymes of gibberellin biosynthesis and a putative negative regulator of gibberellin signal transduction in<Emphasis Type="Italic"> Eustoma grandiflorum</Emphasis>

Eustoma grandiflorum Shinn requires vernalization for the induction of stem elongation and flowering. To investigate the role of gibberellins (GAs) in vernalization, the expression levels of genes encoding enzymes of GA biosynthesis, copalyl diphosphate synthetase, GA 20-oxidase and GA 3-hydroxylase, were examined using two culitvars that show different responses to vernalization. The three genes were induced in a vernalization- and a cultivar-dependent manner. EgSPY, a putative negative regulator of GA signal transduction, was also induced during the vernalization period. The results suggest that the expression of the genes encoding GAs biosynthesis is regulated by vernalization. We postulate that EgSPY functions as a negative regulator of GA signal transduction during vernalization, inhibiting adventitious shoot elongation during vernalization.Communicated by K.K. Kamo     

Genetic adaptation for vernalization requirement in Nepalese wheat and barley

A large number of accessions of covered and naked barley from eastern Nepal were grown without vernalization, and it was found that naked barley accessions were predominantly spring varieties while covered barley accessions were predominantly winter varieties. Seven accessions were subjected to a range of vernalization periods. Four naked varieties were spring varieties, although one showed some response to vernalization, but the three covered barleys were winter varieties. Although the majority of naked barleys are spring forms, they are winter sown at high altitudes and this does not conform to the distribution of naked barley described by Takahashi (1955). Wheat accessions which came from villages situated at high altitudes tended to have higher vernalization requirements than those which came from lower altitudes. This was taken to indicate local adaptation and a low movement of seeds (gene-flow) between villages. The relationship between vernalization requirement and altitude was not found in barley. Marked but contrasting regional patterns for vernalization requirement occurred in the wheat and covered barley. It was concluded that gene-flow was greater within regions than between them. This regional isolation together with environmental heterogeneity are major diversity promoting mechanisms.     

Identification of genes expressed in the shoot apex ofBrassica campestris during floral transition

The vegetative-to-floral transition ofBrassica campestris cv. Osome was induced by vernalization. Poly(A)+RNA was isolated from the transition shoot apex after 6 weeks of vernalization, the floral apex after 12 weeks of vernalization and the expanded leaves just before vernalization, and cDNAs were synthesized. These cDNAs were used for subtraction and differential screening to select cDNA preferentially present in the transition and floral apices. Nucleotide sequences of the resulting 14 cDNA clones were determined, and northern blot analysis was carried out on six cDNAs. Two cDNA clones which did not show significant similarity to known genes were shown to be preferentially expressed in the floral apex.     

Relationships among vernalization, shoot apex development and frost tolerance in wheat

BACKGROUND AND AIMS: Frost tolerance of wheat depends primarily upon a strong vernalization requirement, delaying the transition to the reproductive phase. The aim of the present study was to learn how saturation of the vernalization requirement and apical development stage are related to frost tolerance in wheat. METHODS: 'Mironovskaya 808', a winter variety with a long vernalization requirement, and 'Leguan', a spring variety without a vernalization requirement, were acclimated at 2 degrees C at different stages of development. Plant development (morphological stage of the shoot apex), vernalization requirement (days to heading) and frost tolerance (survival of the plants exposed to freezing conditions) were evaluated. KEY RESULTS: 'Mironovskaya 808' increased its frost tolerance more rapidly; it reached a higher level of tolerance and after a longer duration of acclimation at 2 degrees C than was found in 'Leguan'. The frost tolerance of 'Mironovskaya 808' decreased and its ability to re-acclimate a high tolerance was lost after saturation of its vernalization requirement, but before its shoot apex had reached the double-ridge stage. The frost tolerance of 'Leguan' decreased after the plants had reached the floret initiation stage. CONCLUSIONS: The results support the hypothesis that genes for vernalization requirement act as a master switch regulating the duration of low temperature induced frost tolerance. In winter wheat, due to a longer vegetative phase, frost tolerance is maintained for a longer time and at a higher level than in spring wheat. After the saturation of vernalization requirement, winter wheat (as in spring wheat) established only a low level of frost tolerance.     

Genomic regions controlling vernalization and photoperiod responses in oat

Oat genotypes vary for photoperiod and vernalization responses. Vernalization often promotes earlier flowering in fall-sown but not spring-sown cultivars. Longer photoperiods also promote earlier flowering, and the response to longer photoperiods tends to be greater in cultivars from higher latitudes. To investigate the genetic basis of photoperiod and vernalization responses in oat, we mapped QTLs for flowering time under four combinations of photoperiod and vernalization treatments in the Ogle 2 TAM O-301 mapping population in growth chambers. We also mapped QTLs for flowering time in early spring and late-spring field plantings to determine the genetic basis of response to early spring planting in oat. Three major flowering-time QTLs (on linkage groups OT8, OT31 and OT32) were detected in most conditions. QTLs with smaller effects on flowering were less-consistently observed among treatments. Both vernalization-sensitive and insensitive QTLs were discovered. Longer photoperiod or vernalization alone tended to decrease the effects of flowering-time QTLs. Applied together, longer photoperiod and vernalization interacted synergistically, often on the same genomic regions. Earlier spring planting conferred an attenuated vernalization treatment on seeds. The major flowering-time QTLs mapped in this study matched those mapped previously in the Kanota 2 Ogle oat mapping population. Between these two studies, we found a concordance of flowering-time QTLs, segregation distortion, and complex genetic linkages. These effects may all be related to chromosomal rearrangements in hexaploid oat. Comparative mapping between oat and other grasses will facilitate molecular analysis of vernalization response in oat.     

EFFECTS OF PHOTOPERIOD AND VERNALIZATION ON THE NUMBER OF LEAVES AT FLOWERING IN 32 ARABIDOPSIS THALIANA (BRASSICACEAE) ECOTYPES

The extent of natural variation among wild type Arabidopsis thaliana L. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32 Arabidopsis ecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and nonvernalized plants were transplanted into 8- (short-day) and 20-hour (long-day) photoperiods in controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.     

Vernalization-induced changes of the DNA methylation pattern in winter wheat.

Vernalization is a cold treatment that induces or accelerates flowering and insures that temperate-zone plants will not flower until after winter. There is evidence that vernalization results in DNA demethylation that induces flowering. Differences in DNA methylation can be determined using methylation-sensitive amplified fragment length polymorphisms (AFLPs). Methylation-sensitive AFLPs utilize restriction enzyme isoschizomers that are differentially sensitive to methylation, producing polymorphisms related to methylation differences as opposed to sequence differences. Near-isogenic lines (NILs) have been developed for spring vs. winter habit in wheat (Triticum aestivum) and allow for the study of a single vernalization locus. In this study, differences in the methylation pattern were determined for spring and winter NILs, as well as for unvernalized and vernalized individuals. Winter wheat was more highly methylated than spring wheat and methylation-related AFLPs were produced between winter and spring wheat. Changes in the methylation pattern were observed at the end of vernalization, one week after the end of vernalization, and four weeks after the end of vernalization of winter wheat. However, the most methylation differences were observed one week after removal of winter wheat from cold treatment. Our data suggest that there is not only a vernalization-induced demethylation related to flower induction, but there is also a more general and non-specific demethylation of sequences unrelated to flowering. Two methylation-related AFLPs induced by vernalization were shared among all of the winter NILs.