The Preliminary Research On The Mechanism Of Color Variation In Bamboo Culms

Phyllostachys vivax cv.aureocaulis is a widely planted ornamental bamboo with evergreen leaves.Its glossy culm is golden-yellow randomly marked with narrow and broad green stripes(or rarely light green with yellow stripes).It has great a high value for appreciating and researching.In this study we investigated the growth and development phenotype of it and tried to uncover the molecular mechanism under this color variation by observing the pigments distribution and chloroplast ultrastructure in two sample with different color culms.Besides,we constructed two suppressions subtractive hybridization library constructed from green culm and yellow culm mRNA samples.The main research results were as follows:1 In natural environment,the proportion of Phyllostachys vivax cv.aureocaulis with green culms is about 86%,that means a low incidence of atavism.Period for bamboo shooting was about 16 days and the high growth was about 10 days.2 Neither stroma lamella nor grana lamellas were observed in plastids in the cells of the yellow tissue while complete chloroplasts are observed in the green tissue.Besides,chlorophyll a and b are mainly distributed in the ground tissue under epidermis and in the cells around the bundle sheath in the green part of the internodes.3 The amount of chlorophyll in the cross-section of the green part of culms was significantly higher than that in the yellow part.However,carotenoid was hardly detected in both samples.4 Total lipids in the epidermis of green culms was 4.71% on dry weight and 3.78% in the epidermis of yellow culms.The dry lipids sample showed a grease sheen and a color same with the epidermis.5 1350 ESTs in forward library and 1438 ESTs in reverse library were sequenced.Among those spliced ESTs,578 and 901 ESTs hit known homologous sequences by Blastx against NCBI nr database,a classification of gene annotations showed that the proportion of gene whose functions are characterized in response to stimulus,cellular component,catalytic,binding and development has significant difference between those two cDNA libraries.6 We found that the expression levels of 7 ESTs,including light-harvesting complex gene 1,light-harvesting complex gene 6 and A20/AN1-like zinc finger family gene have significantly higher expression level in green sample than that in yellow sample,while acyl carrier protein gene 3,actin-binding FH2 family gene,Metallothionein 1C and Serine/threonine kinase gene shows a higher level in yellow sample.These genes are commonly thought to play a role in this type of color variation in plants.Current results indicate that the photosynthetic membrane proteins have been destroyed and the photosynthetic membrane lipids of the chloroplast are insufficient in the yellow tissue.These could lead to the yellow appearance on the culms of Ph.vivax cv.aureocaulis.