Poster: Reproductive Development

Abs # 475: Cloning and characterization of flower development genes in papaya

Presenter:	Yu, Qingyi , qyu@hawaii.edu
Authors	Yu, Qingyi  (A) (B)  Moore, Paul H (C)   Ackerman, Christine  (A)   Albert, Henrik H (C)   Paull, Robert E (D)   Ming, Ray  (A)
Affiliations:	(A): Hawaii Agriculture Research Center, Aiea, HI 96701 (B): Department of Molecular Biosciences and Biosystems Engineering, University of Hawaii, Honolulu, HI 96822 (C): USDA-ARS, Pacific Basin Agricultural Research Center, Aiea, HI 96701 (D): Department of Tropical Plant and Soil Sciences, University of Hawaii, Honolulu, HI 96822

Instability of papaya flowers, revealed by environmentally influenced sex reversal and stamen carpellody, results in fruit malformation making it unmarketable. Based on knowledge of flower development in the model plants Antirrhirum and Arabidopsis, we are characterizing homologous genes associated with carpel development in papaya. The Arabidopsis class C organ identity gene AGAMOUS has a papaya homolog named PAG that shares 85% identity with AGAMOUS within the MADS box and K box domains. Genomic Southern analysis showed that papaya has only one copy of PAG that is expressed at a high level in carpels. The Arabidopsis gene LEAFY, a positive regulator of AGAMOUS, has a papaya homolog PFL that shares 65% identity with LFY. PFL encodes a protein sharing 71% identity with the LFY homologs of the two tree species California sycamore (Platanus racemosa) and black cottonwood (Populus trichocarpal). Despite extensive sequence similarity in two conserved regions, the proline-rich and acidic motifs differ between PFL and its LFY counterparts from other plants. This difference may not affect the gene function as demonstrated by research on the Pinus radiata LFY homolog Needly. Genomic and BAC Southern analyses indicate that like PAG, PFL exists as a single copy in the papaya genome. In situ hybridization result showed that PFL is expressed at a relatively low level in the shoot apical meristem of very young seedlings but it is expressed at a high level in the floral meristem. Hua1, another regulator of stamen and carpel identities, has a papaya homolog named Phua that shares about 82% identity with the Arabidopsis Hua1 gene. Understanding the papaya floral development process could lead to strategies for controlling these problems of fruit production.