Jingbo Hu

© 2017 American Society of Plant Biologists. All rights reserved.Aliphatic and aromatic lipids are both essential structural components of the plant cuticle, an important interface between the plant and environment. Although cross links between aromatic and aliphatic or other moieties are known to be associated with the formation of leaf cutin and root and seed suberin, the contribution of aromatic lipids to the biosynthesis of anther cuticles and pollen walls remains elusive. In this study, we characterized the rice male sterile mutant, defective pollen wall 2, which showed an abnormal anther cuticle, a defective pollen wall, and complete male sterility. Compared with the wild type, dpw2 anthers have increased amounts of cutin and waxes and decreased levels of lipidic and phenolic compounds. DPW2 encodes a cytoplasmically localized BAHD acyltransferase. In vitro assays demonstrated that recombinant DPW2 specifically transfers hydroxycinnamic acid moieties, using v-hydroxy fatty acids as acyl acceptors and hydroxycinnamoyl-CoAs as acyl donors. Thus, The cytoplasmic hydroxycinnamoyl-CoA:v-hydroxy fatty acid transferase DPW2 plays a fundamental role in male reproduction via the biosynthesis of key components of the anther cuticle and pollen wall.

Carolina Sartorio has criticized the reasons-responsiveness theory of freedom for being inconsistent with the actual-sequence view motivated by the Frankfurt-style cases. Specifically, reasons-responsiveness conceived as a modal property does not pertain to the actual sequence of the agent's action and thereby it is irrelevant to the agent's freedom and moral responsibility. Call this the challenge of irrelevance. In this article, I present this challenge in a new way that overcomes certain limitations of Sartorio's argument. I argue that the root of the challenge is that reasons-responsiveness as an unmanifested modal property seems to be nonexplanatory for the agent's action. I show that reasons-responsiveness theorists will confront this challenge even if they do not endorse the actual-sequence view. Finally, I deflate this challenge with David Lewis's model of causal explanation, showing that reasons-responsiveness is explanatory in virtue of providing information about the causal history of the agent's action.