春化作用

Autonomous promotion pathway
Mutants of the autonomous pathway (fca, fy, fpa, ld, fld, and fve) are late-flowering in long days and short days, a phenotype that can be overcome by vernalization (these induced mutations, therefore, confer a vernalization requirement) or growth in far-red enriched light . The level of FLC mRNA is increased in these mutants, indicating that the autonomous pathway normally functions to prevent FLC mRNA accumulation.
FRIGIDA (FRI) gene
FRIg::GUS FLCg::GUS
FLCg::GUS + FRI
-Vernalization
+Vernalization
FRIGIDA expression is observed in the shoot and root meristematic regions. FRIGIDA up-regulates FLC expression in these regions and it is this expression that is antagonised by vernalization.
第十六章 植物的温控发育
几个概念
植物生长的温度三基点 cardinal temperature 温周期现象 thermoperiodicity
雪莲 Snow Saussurea
激烈火球菌 Pyrococcus furiosus
春化作用 vernalization
春化作用的概念 春化作用的性质 春化作用的机制
春化作用的性质
有效低温与春化时间 去春化作用,再春化作用 去春化作用,
有效低温与春化时间
春化作用的机理
春化作用的感受时期和感受部位 春化素(vernalin) 春化素( ) 春化作用的分子机理
Features of vernalization
Occurs at shoot meristem Requires several weeks of exposure to low temperatures. Effects of vernalization maintained through many mitotic divisions. Effects of vernalization reset at meiosis.
Expression of FLC. a) Constitutive expression of FLCis sufficient to block flowering (35S is a strong constitutive viral promoter). b) Although FLCis present in early flowering accessions of Arabidopsis it is not expressed to high levels. Late-flowering biennial-like accessions contain dominant alleles of FRI that cause FLCto be highly expressed. Following a vernalizing cold treatment, FLCis permanently downregulated
春化作用的概念和类型
春化作用的定义 植物对低温反应的类型
小麦的冬性, 小麦的冬性,半冬性和春性品种
Lysenko (1898-1976)
A cabbage plant that had been grown in the greenhouse for 5 years. Cabbage is a biennial and requires exposure to prolonged winter cold in order to flower the second spring after planting. The large cabbage has never been exposed to winter and therefore cannot flower.
FRI repression pathway
The plant (left) contains FRIGIDA; the parent plant (right) was used in the transformation experiments. The photograph was taken once both plants had flowered - several months after sowing (left), and 3 weeks after sowing (right). Plants carrying FRIGIDA flower extremely late, but the late flowering is reversed by vernalization.
No vernalization 8 weeks vernalization Santa Fe(winter annual)
Columbia(Summ er annual)
Genetic Analysis of Crossing between Columbia and Santa Fe
Late flowering Columbia Santa Fe Sf x Col 0 40 135 Early flowering 55 0 46
FRI plant – very late flowering Mutagenise with radiation Screen for early flowering plants
3 loss of function Alleles of FRI
4 loss of function Alleles of FLC
Landsberg erecta
Columbia
RLD
These flower in a cold-indpendent manner after producing ~5-15 rosette leaves.
Arabidopsis flowering time mutants. Two Arabidopsis plants, sown at the
FLC 基因 C) (Flowering Locus C)
Localization of FLC by GUS staining
FLC encodes a MADS-boxMADS-boxcontaining protein
It functions in transcriptional regulation. The activity of FLC is semidominant, and transgenic plants containing extra copies of the FLC genomic sequence never flower without vernalization, acting in essence as biennials.
ຫໍສະໝຸດ Baidu
FCA Gene
Mutants carrying recessive alleles of FCA are late flowering and, again, this is reversed to early flowering by vernalization.
RT-PCR analyses of VIN3 and FLC mRNA levels during cold treatment (modified from Sung & Amasino, 2004). Lane 1 (0 days V), seedlings were not exposed to cold. Lane 2 (0 days V-T0), seedlings were exposed to cold for 10 days and harvested for RNA isolation without exposure to warm temperature. Lanes 3 and 4, same as Lane 2 except that seedlings were exposed to cold for 20 and 40 days. Lane 5 (40 days V-T10), after 40 days of cold treatment vernalized seedlings were grown for 10 days at 22°C before harvesting. Although 10 days after vernalization is shown in the last lane, we have found that VIN3 mRNA becomes undetectable within 3 days of growth at 22°C
春化素( 春化素(vernalin) )
矮牵牛
天仙子
SD
LD
GA+SD
春化作用的分子机理
Natural ecotypes of Arabidopsis behave as winter annuals
Commonly-used, early-flowering genotypes of Arabidopsis
same time. The plant on the left is already flowering, whereas the plant on the right is delayed because it carries active FRI.
Sante Fe and Columbia Analysis
Indicates 3:1 segregation with late flowering dominient
Gene Mapping of late flowering gene, FRIGIDA
FRI encodes a 609 amino acid protein of unknown function containing two coil-coil domains implicated in protein protein nteraction.
Summary
FLC is one of the key genes that plays a dominant role in vernalization. FRI gene function cooperatively with FLC Autonomous pathway normally functions to prevent FLC mRNA accumulation. The other genes involved in vernalization are VRN1 and VRN2 which downregulate the activity of FLC Also a major player in this process is DNA methylation.
The DEAN Group
Department of Cell and Developmental Biology, John Innes Centre, UK
A local model for the regulation of flowering by FLC. FLC.
FRIGIDA repression pathway Autonomous promotion pathway Vernalization Promotion Pathway