On the cover: In this issue, Carella et al. (pages 2282–2294) explore the response of an early divergent non-vascular plant, the liverwort, to infection with an oomycete pathogen. Comparison to an evolutionarily young flowering plant reveals conserved features indicative of an ancestral pathogen deterrence strategy centered on phenylpropanoid-mediated biochemical defenses. The image shows sporophytes of the umbrella liverwort (Marchantia polymorpha) hanging upside down beneath the archegoniophore. Image by David Hoey.
新植物学家：南京农大揭示MYC2调控植物毛状体形成的作用机制
毛状体（Trichomes）是陆地植物外表皮的一种特殊的突起结构。 本研究以杭菊为研究对象探索毛状体的形成机制。首先作者以无毛状体和正常叶片的转录组触发，发现转录因子CmMYC2正调控 T-shaped 和 glandular 毛状体的发育，同时还参与了glandular trichomes的萜类化合物的累积。
CmMYC2对毛状体发育的形成以及萜类化合物的累积的调控受到它与 CmMYBML1的互作的调控.
小结：本研究揭示了MYC2转录因子在毛状体和萜类化合物合成过程中的作用。
A conceptual model of enhancing chrysanthemum trichomes density and trichome-stored terpene content mediated by CmMYC2–CmMYBML1 module to achieve the resistance to Spodoptera litura larvae feeding. As a response to the MeJA treatment, the expression of CmMYC2 was promoted to trigger two divergent pathways in trichome formation and terpene synthesis. ① CmMYC2 directly activated the expression of CmMYBML1 to increase the density of both T-shaped and glandular trichomes. Meanwhile, CmMYBML1 directly upregulated the expression of CmTPS9/CmTPS12 to synthesize trichome-stored terpene compounds. The enhanced trichome density and constitutive terpenoid accumulation synchronously contributed to physical and chemical defense against S. litura larvae infestation. ② As the accumulation of CmMYBML1 protein, excessive CmMYBML1 could bind with CmMYC2 as the heterodimer complex, which weakened the efficiency of CmMYC2 in the activation of CmMYBML1 expression. Hence, a self-feedback regulation mediated by CmMYBML1 in the trichome development and terpene synthesis for resisting the insect was formed. Overexpression of CmMYC2 led to the increasing of IAA level that may directly determine the trichomes formation. Solid lines represent the steps validated in this study and dashed line represents the hypothetical step. Rectangles represent the genes, while ovals represent the corresponding proteins.
原文：CmMYC2–CmMYBML1 module orchestrates the resistance to herbivory by synchronously regulating the trichome development and constitutive terpene biosynthesis in Chrysanthemum
