Identification and Characterization of Genes Differentially Expressed in Phalaenopsis aphrodite Roots under Nutrient Deficiency Stress, Poster Board #262

Phalaenopsis aphrodite Rchb. f. is an epiphyte native to tropical broadleaf forest in Taiwan. Epiphytic roots attach to the surface of tree trunks instead of growing in soil. Unique structures and morphology of Phalaenopsis roots include velamen outside epidermis, passage cells in endodermis, absence of root hairs, and lack or absence of branch roots. Understanding the mechanism of nutrient uptake and metabolism in Phalaenopsis is important to determine how efficient nutrient usage is achieved under intermittent supply. Phalaenopsis Sogo Yukidian ‘V3’ was fertilized with various deficient concentrations of N, P, and K every 2 weeks. After 8 weeks of treatment in 30/25°C, plants were transferred to 25/20°C to induce spiking. No apparent phenotype differences were observed from treatments of N, P, or K deficiency after 8 weeks in the vegetative stage. However, the treatments affected spiking rates dramatically and deficiency symptoms started to show on the leaf after flowering. Microarray analysis revealed differential gene expression in roots. There were 11 up-regulated and 37 down-regulated genes commonly appearing in roots under N, P, or K deficiency stress. The transcript level of a phosphate transporter increased significantly under phosphate deficiency. One of the zinc finger transcription factors, GATA, increased under N, P, or K deficiency stress. Mineral contents between treatments were analyzed using inductively coupled plasma spectroscopy. Leaf iron concentration was lower under phosphate deficiency.