Yifan Sun

© 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.

Quasi-realists have proposed an “internal” reading of the mind-independence claim embedded in our moral discourse, according to which the claim to mind-independence itself is a moral claim. I argue against such a quasi-realist “internal” reading. My objection is that quasi-realists cannot plausibly explain why the majority of us, either implicitly or explicitly, take moral mind-independence to be a metaethical notion. Quasi-realists either must attribute a quite obvious mistake to most metaethical theorists without explaining why they cannot recognize it, or give us an intolerably ad hoc explanation about why ordinary moral speakers fail to understand their own words. Without properly addressing this problem, we have good reason to reject the quasi-realist account of moral mind-independence.

A non‐normative, response‐dependent view about morality can avoid metaphysical extravagance and explain why the extension of some non‐normative concepts can non‐accidentally match the extension of moral concepts. These features make it a plausible reductive account of moral properties. However, some philosophers believe that a response‐dependent account of morality must contain an irreducibly normative component. I argue that it is impossible to defend such a position while retaining the response‐dependent nature of morality in the ordinary sense. However, I believe that philosophers' motivation for engaging in such a philosophical project should be taken seriously. The underlying concern is that the plausibility of a response‐dependent view makes people's strong commitment to irreducible normativity a puzzle that requires an explanation. I explain why people systematically fail to give up this commitment without claiming that they rationally cannot give it up, which means a non‐normative response‐dependent view is immune from such a challenge.