ASYMMETRIC LEAVES1 and REVOLUTA are the key regulatory genes associated with pitcher development in Nepenthes khasiana

Nepenthes develops highly specialized insect-eating organs called pitchers that provide adequate insect-derived nutrients to the plants to offset low nutrient availability in their natural habitat. But so far, the molecular basis of Nepenthes pitcher development remains largely unknown. In an attempt to unravel the underlying mechanisms of pitcher formation, we made morphological observations of the developing N. khasiana leaf and performed RNA-seq to identify genes controlling pitcher development. Histology and scanning electron microscopy photomicrographs show that pitcher formation in N. khasiana occurs early in development and shares anatomical features with the young in-rolled leaf base lamina. Analysis of the RNA-seq data indicated that the modification of the leaf into a pitcher is associated with the altered expressions of leaf polarity genes ASYMMETRIC LEAVES1 (AS1) and REVOLUTA (REV). In fact, both genes displayed exclusive or relatively higher expressions in the tip of the leaf that later developed into a pitcher. We propose that NkAS1 may act to inhibit lamina outgrowth and promote the formation of the tendril. Increased NkREV expression may have been involved in the formation of the N. khasiana pitcher. This dataset will allow further research into this area and serve as the basis for understanding Nepenthes pitcher development.