The Molecular Basis Of Leaf-color Difference Between Yellow-leaf And Green-leaf Ginkgo

Ginkgo(Ginkgo biloba L.), an ancient and precious plant, is the only one specie of Ginkgopsida and deciduous broad-leaved gymnosperm. It takes a special role in plant evolution and is an interesting study area for scientists. Meanwhile, Ginkgo is an important species with medical, timber, nuts and ornamental function, which has been planted in most areas of China. In this study, we selected the yellow-leaf ginkgo, a Spontaneous mutation, which was selected by researchers in Nanjing Forestry University. Yellow-leaf ginkgo was gradually applied in garden landscape project by the special gold leaves in spring. Hence, it is necessary to study the difference of yellow and green ginkgo on molecular level and good for revealing coloration mechanism of yellow ginkgo. Meanwhile, we test the adaptive difference of the two ginkgos under high temperature and light intensity, it provide a reference for planting and popularizing the new variety. The conclusion of this paper was shown as follow:1. Yellow ginkgo has another viewing period by detecting leaf-color of these two varieties during one year using RHSCC(Royal Horticultural Society Color Chart) and Konica Minolta CR-210. The viewing period is from the early of April to the middle of March. Leaf-color of yellow ginkgo was gold-yellow at this period. The lightness of color(L*) was the maximum value during one year and the chromaticity of color(C*) value was larger than the follow period.2. The leaf-change of yellow ginkgo was just related to chlorophylls content in leaves by testing the contents of pigments(chlorophylls and carotenoids). The chlorophylls were low from the early of April to the middle of March. Correlation analysis revealed that leaf-color parameters of yellow ginkgo was significant related to chlorophylls contents.3. The development of chloroplast in yellow and green ginkgo was detected by transmission electron microscope. The result revealed that the chloroplast development of yellow gingko was later than green one, while the chloroplast degradation of yellow one was earlier than green one.4. RNA sequence was implemented by Illumina high-throughput sequencing and 595127 unigenes were obtained and annotated by six nucleotide or protein databases(NCBI non-redundant nucleotide sequences, NCBI non-redundant protein sequences, SwissProt protein sequences, Clusters of Orthologous Groups of proteins, Gene Ontology database and KEGG Ortholog database). 220 differential expressed unigenes and 358 unigenes included different SNP sites in CDS region were got by comparing transcriptome of these two varieties. All the above unigenes were annotated using GO and KO database, then total 70 unigenes involved in chloroplast development and pigments metabolism were selected. These unigenes provided a reference for revealing the causes of yellow leaves in spring.5. We compared the light response curves and chlorophyll fluorescence kinetic curves of the yellow and green ginkgos under different temperatures and light intensities. The results revealed that the threshold value of this two species in April and July were respectively 32℃, 600 μmol m–2 s–1(yellow ginkgo, in April); 40℃,600 μmol m–2 s–1(yellow ginkgo, in July);32℃,1800 μmol m–2 s–1(Green ginkgo, in April) and 42℃,1800 μmol m–2 s–1(Green ginkgo, in July). When the temperature and light intensity are higher than the above value, gingko will suffer unrecoverable stresses.