Research On The Mechanism Of The Leaf Colour Transformation Of Yellow Leaf Colour Mutant 9110Gt In Cucumber(Cucumis Sativus L.)

Cucumber (Cucumis sativus L) is an important annual crop belonging to the Cucubit family. China is the widest area of growing cucumber and the highest total yield in the world. The leaf colour mutant is an ideal material of research on the photosynthetic system structure, function and regulation mechanism, and it has high application value in the aspect of breeding. Currently, research on leaf colour mutant of cucumber focused on physiology, genetics. Previous reports only introduced incidence, classification and inheritance of mutant, but the mechanism of the leafcolour transformation of mutants is ambiguity.The new leaf colour mutant 9110Gt of cucumber was used in this study. The ultrastructural of chloroplast, photosynthetic pigment composition and content, Pchl content and external factors of mutant 9110Gt was analysed. Furthermore, the used of cDNA-AFLP and cDNA-Ad-SRAP technology obtained transcript derived fragments. All the studies were supposed to provide the mechanism of the leafcolour transformation of yellow leaf colour mutant 9110Gt. The brief results of this paper were summed as follows:1. The ultrastructure of chloroplast were observed by submicroscopy. The result showed that 9110Gt's chloroplast structure developed incomplete, and it's metabolic capacity was lower than normal, and it assimilation product less. But with the color change to green, the chloroplast structure of mutant had growth and development, the density and aggregation of thylakoids and ability to catch light has been increase .The grana lamella was mainly cause of Mutant chlorophyll content to reduce and eventually lead to the leaf yellow color.2. Spectral analysis showed that pigment component of mutant wasn't obvious changes. Photosynthetic pigment content of mutant were lower than normal in yellow period.The yellow leaf color was due to the decreasing of the chlorophyll. The protochlorophyll of mutant was lower than mutant turn green. With the color of leaf turning into green, chlorophyll biosynthesis capability of mutant has been enhanced. We can concluded that there was a blockage in the chlorophyll biosynthesis of mutant.3. The result of Photosynthetic capacity showed that the photosynthetic capacity of normal was stronger than the mutant .The non-stomatal factors was mainly cause of net photosynthetic rate decrease. This was due to chlorophyll biosynthesis was blocked, the chloroplast's photosynthetic functions decline, thus affecting the mutant net photosynthetic rate, making mutant photosynthetic capacity lower.4. 9110Gt is temperature-sensitive mutant. The temperature effect leaf color transformation. With temperature increased, photosynthetic pigment and Pchl content of mutant was improved. The photoperiod also effect leaf color transformation. With the photoperiod increase, the photosynthetic pigment and Pchl content of mutant was increased. But the light intensity had little influence on leaf color transformation.5. cDNA - AFLP and cDNA - Ad - SRAP was used to detect differentially expressed genes during the mutant yellow period, totally 9 candidate transcript derived fragments were obtained. The 4 candidate transcript derived fragments had highly identities with cucumber mitochondrial MSC16 genes, tRNA-Arg gene and 4.5SrRNA gene in Cucumis sativus chloroplast complete genome. We suggested these genes were related to the expression of yellow leaf colour.