Studies On Molecular Mechanisms Of Narciclasine Of Natural Bioactive Substance In The Post-embryonic Development Of Arabidopsis Thaliana Root

Many substances that naturally present in plants can alter plant growth and development. Narciclasine (NCS) is an Amaryllidaceae alkaloid isolated from Narcissus tazetta bulbs with a broad range of biological activities. Nevertheless, the mechanism of NCS action in plant cell has remained largely elusive. Here, we investigated the effects of NCS on postembryonic development of Arabidopsis root.1. Results showed that the cell division was inhibited by NCS, and cell differentiation in root tip was also affected by NCS in a concentration dependent manner. By using quantitative reverse transcription PCR and cell cycle kinase (CDK) activity assay, we found that NCS at low concentration preferentially targets mitotic cell cycle specific/cyclin complexes, whereas at high concentration the strong accumulation of KRP1 and KRP2 protein affects the CDKA1:1/cyclin complexes with a role both in G1/S and G2/M phase. Thus, for these reasons, NCS can differently affect cell division and differentiation of Arabibdopsis root cells in a concentration dependent manner.2. Furthermore, seedlings grown on NCS showed defects in root gravitropism. These phenotypes correlate with a reduction in auxin transport in Arabidopsis root. Expressions of auxin transport genes were differently affected by NCS, and the polar localization of PIN2 protein was altered after application of NCS. Taken together, we propose that NCS modulates auxin transport gene expression and PIN2 localization, thus inhibits auxin transport and affects auxin distribution necessary for postembryonic development of Arabidopsis root.