Poster: Reproductive development

Abs # 356: Isolation and Developmental Characterization of a COP8 Orthologue in Germinating Lily Pollen

Presenter:	Jauh, Guang-Yuh , jauh@gate.sinica.edu.tw
Authors	Jauh, Guang-Yuh  (A)   Hsu, Chia-Mei  (A)   Jiang, Yi-Chi  (A)   Huang, Jong-Chin  (A)
Affiliations:	(A): Institute of Botany, Academia Sinica

Lily (Lilium longiflorum Thunb. cv Avita) pollen stored at -20„aC for 2 months significantly delayed the germination/growth rates. Total protein profiles showed significantly different, qualitatively and quantitatively, as well. Suppression subtractive hybridization screening was used to clone mRNAs essential for pollen germination/growth. More than 100 cDNAs were obtained after screening and 19 were chosen for further characterization. Northern blotting indicated that most of these 19 gradually disappeared during -20¢XC storage. Full recovery of these transcripts was achieved by incubating the stored pollen grains in germination medium for 2 hours. A cDNA encoding a lily COP8 orthologue (LLCOP8) was chosen for further investigation. COP8 is one component of COP9 signalosome, which functions as a nuclear repressor involved in various developmental aspects of higher eukaryotes. The amino acid sequence of LLCOP8 showed high identity (79%) and similarity (89%) to Arabidopsis COP8. To characterize the possible function of LLCOP8 in germinating pollen, temporal protein expression and sub-cellular localization were taken. Immunogold studies revealed that LLCOP8s was present in the cytosol and nucleus of both vegetative and generative cells, and also developmentally accumulated in amyloplasts of germinating lily pollen. LLCOP8 was also found in the starch granules of stylar transmitting-tract epidermis and in vivo-grown tube cells. Ultra-structural observation revealed that these amyloplasts, containing starch granules and other organelles such as mitochondria, were enclosed by tubular endoplasmic reticulum. Possible autophagic machinery was proposed for the degradation of reserve materials, such as starch granules, during pollen germination.