Anatomical and physiological differences and differentially expressed genes between the green and yellow leaf tissue in a variegated chrysanthemum variety.

The leaves of the chrysanthemum variety 'NAU04-1-31-1' are variegated with distinct green and yellow sectors. The chlorophyll content of the yellow leaf tissue is less than that in the green one. The chloroplasts in the yellow leaf tissue were vacuolated, lacked thylakoid membrane structure and contained clusters of plastoglobuli with few or no starch grains. The yellow leaf tissue was more sensitive to photo-inhibition than the green leaf tissue. Suppression subtractive hybridization (SSHs) libraries were constructed to identify genes which were differentially transcribed in the two tissue types. The sequencing of 339 SSH clones identified 150 unigenes (93 singletons and 57 contigs), of which 85 were differentially transcribed in the green leaf tissue and 65 in the yellow leaf tissue. Unigenes associated with photosynthesis were particularly frequent, and many of these genes were up-regulated in the yellow leaf tissue. Both CmChlH which encodes the large subunit of Mg-chelatase and CmFtsH (ATP-dependent metalloprotease) were up-regulated in the yellow leaf tissue, and their transcription was regulated by light.