Wenjin Liu

© 2016 American Society of Plant Biologists. All rights reserved.Calcium/calmodulin-dependent protein kinase has been shown to play an important role in abscisic acid -induced antioxidant defense and enhance the tolerance of plants to drought stress. However, its downstream molecular events are poorly understood. Here, we identify a NAC transcription factor, ZmNAC84, in maize, which physically interacts with ZmCCaMK in vitro and in vivo. ZmNAC84 displays a partially overlapping expression pattern with ZmCCaMK after ABA treatment, and H2O2 is required for ABA-induced ZmNAC84expression. Functional analysis reveals that ZmNAC84 is essential for ABA-induced antioxidant defense in a ZmCCaMK-dependent manner. Furthermore, ZmCCaMK directly phosphorylates Ser-113 of ZmNAC84 in vitro, and Ser-113 is essential for the ABA-induced stimulation of antioxidant defense by ZmCCaMK. Moreover, overexpression of ZmNAC84 in tobacco can improve drought tolerance and alleviate drought-induced oxidative damage of transgenic plants. These results define a mechanism for ZmCCaMK function in ABA-induced antioxidant defense, where ABA-produced H2O2 first induces expression of ZmCCaMK and ZmNAC84 and activates ZmCCaMK. Subsequently, the activated ZmCCaMK phosphorylates ZmNAC84 at Ser-113, thereby inducing antioxidant defense by activating downstream genes.

Ignorance is commonly assumed to be a lack of knowledge in Plato’s Socratic dialogues. I challenge that assumption. In the Protagoras, ignorance is conceived to be a substantive, structural psychic flaw—the soul’s domination by inferior elements that are by nature fit to be ruled. Ignorant people are characterized by both false beliefs about evaluative matters in specific situations and an enduring deception about their own psychic conditions. On my interpretation, akrasia, moral vices, and epistemic vices are products or forms of ignorance, and a person who lacks knowledge is not necessarily ignorant.