Abstract

With over 25,000 species, Orchidaceae represents one of the largest and most diverse families of flowering plants. In addition to the unique aspects of developmental reproductive biology and the specialized pollination and ecological strategies of orchids, development of new hybrids is economically important to floricultural industries. Wild orchids are especially susceptible to increasing anthropogenic disturbances, and all members of this family are threatened or endangered in their wild state. Like other threatened plant species, long-term seed storage in seed banks is crucial for the preservation of this family. Unfortunately, such storage will not be successful until the complex seed biology of orchids is understood. Our aim is to contribute to the understanding of orchid seed biology and hence the design of seed banking protocols for this family. Plant seeds are divided into two large groups. So-called orthodox seeds dry out as a natural part of development to as low as 5% (fresh weight basis) water at the end of maturation. Orthodox seeds require low water contents and temperatures for storage. On the other hand, recalcitrant seeds can not be dried without compromising their internal structural integrity and storage at low water contents would be deadly for these seeds. At present, it is unclear whether orchid seeds are orthodox or recalcitrant. While their exact role in embryogenesis is ambiguous, the accumulation of late embryogenesis abundant (LEA) proteins often has been implicated with the acquisition of desiccation tolerance in orthodox seeds. In hopes of better understanding the acquisition of desiccation tolerance in orchid seeds our short term goal was to identify members of the LEA protein gene family. Hybrids of the genus Phalaenopsis are among the top-traded blooming potted plants worldwide. However, despite the unique aspects of this species, relatively few molecular studies have focused on them. Using the limited genomic orchid resources available, we were able to design primers to successfully isolate cDNA clones of representatives of four unique LEA protein genes from hybrid Phalaenopsis plants. Using the sequences obtained from this work, we hope to utilize quantitative-PCR to monitor the expression of these 4 LEA gene transcripts at varying stages of seed development and drying conditions. This work will hopefully help to elucidate the function of LEA proteins in orchid embryogenesis and contribute to the construction of a successful seed banking protocol for orchids.