Involvement of a novel NAP member LbNAP in flower senescence and dehydration stress in cut lily

Abstract

In Arabidopsis thaliana, NAC-like and activated by AP3/PI (NAP) are NAC transcription factors that regulate leaf senescence and environment stress. Gene LbNAP, which has a typical NAC region, was cloned from lily petals. Our results indicated that LbNAP was located in the nucleus, and the gene had transcriptional activation activity. Further studies on LbNAP expression showed that it was lowest in green buds and highest in aging petals during bud development. Silencing of LbNAP in buds using virus-induced gene silencing resulted in a delayed senescence phenotype and less dehydration stress injury, which were related to the increase in catalase and superoxide dismutase activities and expression of their genes. Over-expression of LbNAP in A. thaliana (OE-LbNAP) resulted in slow root growth and decreased fresh weight. When treated with 250 mM mannitol, root length and fresh weight of transgenic seedlings were significantly lower than those of wild type. In addition, flowers of OE-LbNAP showed earlier senescence and weaker dehydration tolerance; when OE-LbNAP plants were subjected to 7 days of drought stress, their survival rate was significantly lower than that of the wild type. These results suggest that LbNAP was positively involved in age-induced flower senescence and dehydration stress.