Variations of salt stress responses and functional identification of TgPYR1-like8 in Tulipa gesneriana

Tulip cut flowers are mainly produced through hydroponic cultivation. The accumulation of nutrient substances in hydroponic solution generally resulted in ion stress and osmotic stress, which in turn affected the growth and ornamental characteristics of tulip plants. This study aimed to evaluate and compare the salt stress sensitivities of tulip cultivated varieties. The results indicated that most of tulip cultivars showed relatively high sensitivity to low concentrations of NaCl treatment, while the root growth and floral stalk elongation were significantly inhibited by 15 mM NaCl and flowering opening was completely prevented under 75 mM NaCl conditions. Salt stress caused differential accumulations of osmotic regulators including proline, soluble sugars and ions concentrations between two contrasting varieties. We further identified the function of TgPYR1-like8 which showed differential expression patterns among tulip cultivars and displayed the most expression abundance in flower petals. TgPYR1-like8 over expressed Arabidopsis lines showed hypersensitivity to salt treatment during seed germination and young seedlings growth when compared with wild-type plant. Transient silencing of endogenous TgPYR1-like8 in tulip petal discs decreased salt sensitivity and delayed salt-induced petal senescence. These findings provide evidences for revealing the function of TgPYR1-like8 in tulip salt stress responses and more clues on how to improve the hydroponic cultivation of different tulip varieties.