The Aquaporin Gene SbPIP1;2 Is Involved in Dormancy Release and Regulated Under Low Temperatures in Lilium ‘Siberia’

The dormancy of lilies is an important physiological process involving vernalisation and the differentiation and maturation of flower buds. We have cloned an aquaporin, SbP1P1;2, from the Lilium ‘Siberia’. Subcellular localisation analysis indicates that it is a protein that is localised to the plasma membrane in Nicotiana benthamiana. VIGS-mediated transient silencing revealed that silencing the SbPIP1;2 gene inhibited the development of lily flower buds, while those in the control group differentiated earlier to the anther primordia stage. Notably, the ABA levels in the control group had dropped significantly by day 63, suggesting that dormancy ended earlier than in the treatment group. The test plants’ phenotype is characterised primarily by the fact that silencing the SbPIP1;2 gene inhibits both flower bud development and root growth. The dormancy-to-sleep transition phase (PS vs. TS) was also the period during which the largest number of differentially expressed genes was observed. KEGG enrichment analysis indicates that starch and sucrose metabolic pathways are most active from the onset to the completion of dormancy release and that significant differences occur in several key genes within these pathways. These include alpha-trehalose-phosphate synthase (TPS), sucrose phosphate synthase (SPS), trehalase (TREH), fructokinase-1 (E2.7.1.1), beta-glucosidase (bglB), glycogen synthase (glgA), glucose-6-phosphate isomerase (GPI), and ectonucleotide pyrophosphatase/phosphodiesterase family members 1 and 3 (ENPP1/3). The discovery that aquaporins promote dormancy breaking in lilies is a highly successful case study for aquaporin research in flowers.