On the cover: Herbivory is a dominant characteristic in beetles, Earth’s most speciose animal group. In this issue, Salem et al. (pages 2875–2886) examined the role of microbial symbionts in upgrading the digestive physiology of tortoise leaf beetles (pictured: Cassida rubiginosa). By combining comparative genomics, biochemical characterizations, and biogeography, the authors describe how variation in a symbiont’s metabolism can impact the ecology of its host. Encoded within highly reduced symbiont genomes are pectin-degrading enzymes. Symbionts endowing their hosts with a greater diversity of digestive enzymes allow their herbivorous hosts to process a greater variety of complex plant polymers. As this upgraded digestive phenotype corresponds to a wider ecological distribution, symbiosis likely contributes to the radiation of herbivorous beetles to exploit, and coevolve with, a correspondingly diverse flora. Image by Hassan Salem.
JXB:德国凯泽斯劳滕大学揭示SWEET17在植物耐受干旱胁迫过程中的作用机制
Sugars Will Eventually be Exported Transporters (SWEETs)是植物体内的一种重要的糖转运子。作为单项转运子，SWEETs 促进了糖分子的跨膜运输并在多种生理过程中发挥重要作用。 AtSWEET17是一个 vacuolar fructose facilitator, 该基因被认为参与了干旱胁迫条件下根系的发育。前人研究显示过表达该基因在苹果中的基因可以显著提高植物对干旱胁迫的耐受性。本研究借助基因表达分析、茎结构分析以及糖的分析，发现SWEET17在碳供给以及茎分支伸长过程中发挥重要作用，这种效应在干旱胁迫导致的碳供给不足的条件下尤为显著。
小结：本研究揭示了SWEET17在干旱胁迫响应过程中的作用机制。
Importance of SWEET17 in carbohydrate distribution from the pith and in cell-to-cell distribution for branch emergence and elongation. SWEET17, a vacuolar fructose facilitator, is important for post-phloem transport of carbohydrates to demanding sink tissues such as meristems of developing cauline branches. There, fructose, derived from sucrose cleavage in the vacuole, stimulates branch outgrowth and elongation by regulation of key integrators such as BRC1 and ACE1. Such carbohydrate distribution seems to be especially impaired in situations of reduced carbohydrate supply such as drought stress. Under such conditions, reserve sugars, accumulated in the pith of the inflorescence stem, seem to be mobilized and exported from the vacuoles of this tissue via SWEET17 to maintain carbohydrate supply to demanding sinks. Created with BioRender.com.
原文：Carbohydrate distribution via SWEET17 is critical for Arabidopsis inflorescence branching under drought
