摘要
Being shaded is a common environmental stress for plants, especial y for densely planted crops. Shade de-creases red: far-red (R:FR) ratios that inactivate phyto-chrome B (PHYB) and subsequently release phytochrome interaction factors (PIFs). Shaded plants display elongated hypocotyls, internodes, and petioles, hyponastic leaves, early flowering and are inhibited in branching: traits col ectively cal ed the shade avoidance syndrome (SAS). ZEITLUPE (ZTL) is a circadian clock component and blue light photoreceptor, which is also involved in floral rhythms and plant defense in Nicotiana attenuata. ztl mutants are hypersensitive to red light and ZTL physical y interacts with PHYB, suggesting the involvement of ZTL in R:FR light signaling. Here, we show that N. attenuata ZTL-silenced plants display a phenotype op-posite to that of the SAS under normal light. After simulated shade, the normal y induced transcript levels of the SAS mar-ker gene, ATHB2 are attenuated in ZTL-silenced plants. The auxin signaling pathway, known to be involved in SAS, was also significantly attenuated. Furthermore, NaZTL directly in-teracts with NaPHYBs, and regulates the transcript levels of PHYBs, PIF3a, PIF7 and PIF8 under shade. Our results suggest that ZTL may regulate PHYB- and the auxin-mediated sig-naling pathway, which functions in the SAS of N. attenuata.
