Poster: Regulation of gene expression

Abs # 737: Characterization of actin genes from Ornithogalum sp.

Presenter:	Maroon-Lango, Clarissa J, maroonc@ba.ars.usda.gov
Authors	Maroon-Lango, Clarissa J (A)   Zhu, Baolong  (A)   Hammond, John  (A)
Affiliations:	(A): USDA-ARS, USNA, Floral and Nursery Plants Research Unit

Great strides have been taken to improve the horticultural features of Ornithogalum spp. (family Liliaceae) by conventional breeding coupled with in vitro ovule-rescue. However, Ornithogalum plants remain highly susceptible to viruses including potyviruses. For genetic transformation with virus-derived genes to confer resistance, it is desirable to use an Ornithogalum-derived promoter to ensure optimal expression in the homologous host. In this regard, putative actin genes were identified from the genomic library of Ornithogalum sp. by hybridization using a heterologous probe derived from the soybean actin gene. Southern blot of restriction fragments from positively hybridizing lambda clones was also probed with the soybean actin gene. Restriction fragments that lit up by hybridization were subcloned into pBSK and sequenced. Four actin genes are being characterized. The full-length sequence of ORACT1 and partial sequences of ORACT2-4 were obtained. Tissue specificity and developmental regulation of at least three members of the actin multigene family are being evaluated in Ornithogalum. To determine promoter activities of untranslated sequences upstream of the actin coding region, constructs were made consisting of translational fusions of actin-derived sequences with the GUS reporter gene. Preliminary assays indicate that transient ORACT1 promoter activity in tobacco protoplasts is a quarter of the strength of CaMV 35S. Results of assays in Ornithogalum and other heterologous species involving electroporation of protoplasts with these constructs will be reported.