Os09g0380200

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Annotated Information

Function

Chlorophyll (Chl) and lutein are the two most abundant and essential components in photosynthetic apparatus, and play critical roles in plant development. In this study, we characterized a rice mutant named young leaf chlorosis 1 (ylc1) from a 60Co-irradiated population. Young leaves of the ylc1 mutant showed decreased levels of Chl and lutein compared to those of wild type, and transmission electron microscopy analysis revealed that the thylakoid lamellar structures were obviously loosely arranged. Whereas, the mutant turns green gradually and approaches normal green at the maximum tillering stage. The Young Leaf Chlorosis 1 (YLC1) gene was isolated via map-based cloning and identified to encode a protein of unknown function belonging to the DUF3353 superfamily. Complementation and RNA-interference tests confirmed the role of the YLC1 gene, which expressed in all tested rice tissues, especially in the leaves. Real-time PCR analyses showed that the expression levels of the genes associated with Chl biosynthesis and photosynthesis were affected in ylc1 mutant at different temperatures. In rice protoplasts, the YLC1 protein displayed a typical chloroplast location pattern. The N-terminal 50 amino acid residues were confirmed to be necessary and sufficient for chloroplast targeting. These data suggested that the YLC1 protein may be involved in Chl and lutein accumulation and chloroplast development at early leaf development in rice.

Expression

Young Leaf Chlorosis 1, a chloroplast-localized gene required for chlorophyll and lutein accumulation during early leaf development in rice. Lutein and b-Car were measured by HPLC according to the described methods (Thayer and Bjorkman 1990). 30 mg of leaves were taken from 10-day-old, 14-day-old and 30-day-old seedlings, and ground in liquid nitrogen and soaked in 1 ml cold 80 % acetone. The samples were placed on ice for 15 min in the dark and then centrifuged for 10 min at 12,000g. The supernatants were transferred to another tube and the pellets were re-extracted with 1 ml cold 80 % acetone, and the above step repeated. The supernatants were combined, measured and passed through a 0.45-lm filter. The extracts were stored at -20 �C or analyzed by HPLC immediately. Mass spectra were obtained using LCMS-2010A with Dupont Non-Endcapped Zorbax C-18 column (4.6 9 250 mm, 5 lm particle size).Mobile phase A was 85 % acetonitrile/15 % methanol; Solvent B was 68 % methanol/32 % ethyl acetate. 50 ll samples were injected at a flow rate 1 ml/min and the peak areas were collected at 440 nm. The standard solution lutein and b-Car were purchased from Sigma.

   For TEM analysis, transverse sections of leaves from 2-week- and 2-month-old plants grown in a paddy field were fixed in a solution of 2 % glutaraldehyde and further fixed in 1 % OsO4. After staining with uranyl acetate, tissues were further dehydrated in an ethanol series, and finally embedded in Spurr’s medium prior to ultrathin sectioning. Samples were stained again and examined with a Hitachi H-7650 transmission electron microscope.

Evolution

Both Chls and Cars were measured using a spectrophotometer according to the method of Arnon (1949) with minor modifications. Briefly, equal weights of freshly collected second top leaves from 10-day-old, 14-day-old and 30-day-old seedlings were marinated in 95 % ethanol for 48 h under dark conditions. Residual plant debris was removed by centrifugation. The supernatants were analyzed with a DU 800 UV/Vis Spectrophotometer (Beckman Coulter) at 665, 649 and 470 nm, respectively.

Labs working on this gene

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1/National Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, China

2/National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China