植物腺毛中防御物质的合成与调控及转运研究进展

植物毛状体来源于表皮细胞的延伸,是表皮细胞的特有结构。植物毛状体可分为腺毛和非腺毛,腺毛是具有分泌作用的毛状体,也是大量次生代谢产物的合成、储存以及释放的场所。植物腺毛常分泌不同类型的防御物质如萜类、氨基酸及苯丙烷类、酰基糖、脂肪类衍生物等,这些次生代谢物质能够保护植物免受生物和非生物胁迫,具有重要的防御作用。该文对近年来国内外有关植物腺毛的类型、防御物质的合成与调控等方面的研究进展进行综述,并重点对其合成途径、调控机理与转运机制的研究进展进行梳理,以期为防御物质的生物合成和遗传改良研究提供参考。     

Bidirectional Secretions from Glandular Trichomes of Pyrethrum Enable Immunization of Seedlings

Glandular trichomes are currently known only to store mono- and sesquiterpene compounds in the subcuticular cavity just above the apical cells of trichomes or emit them into the headspace. We demonstrate that basipetal secretions can also occur, by addressing the organization of the biosynthesis and storage of pyrethrins in pyrethrum (Tanacetum cinerariifolium) flowers. Pyrethrum produces a diverse array of pyrethrins and sesquiterpene lactones for plant defense. The highest concentrations accumulate in the flower achenes, which are densely covered by glandular trichomes. The trichomes of mature achenes contain sesquiterpene lactones and other secondary metabolites, but no pyrethrins. However, during achene maturation, the key pyrethrin biosynthetic pathway enzyme chrysanthemyl diphosphate synthase is expressed only in glandular trichomes. We show evidence that chrysanthemic acid is translocated from trichomes to pericarp, where it is esterified into pyrethrins that accumulate in intercellular spaces. During seed maturation, pyrethrins are then absorbed by the embryo, and during seed germination, the embryo-stored pyrethrins are recruited by seedling tissues, which, for lack of trichomes, cannot produce pyrethrins themselves. The findings demonstrate that plant glandular trichomes can selectively secrete in a basipetal direction monoterpenoids, which can reach distant tissues, participate in chemical conversions, and immunize seedlings against insects and fungi.     

植物表皮毛研究进展

表皮毛是大多数植物地上部分表皮组织所延伸出来的一种特化的毛状结构附属物。表皮毛在植物表皮层和环境间构筑了一道天然的物理屏障, 不但对植物的生长发育具有重要意义, 而且还具有非常高的应用价值和经济价值。近几年, 研究者从不同植物中不断克隆出新的表皮毛发育相关基因, 在揭示植物调控表皮毛生长发育的分子机制方面取得很大进展。该文综述了植物表皮毛的最新研究进展, 并展望了植物表皮毛的研究方向及应用开发价值。     

Identification, functional characterization and developmental regulation of sesquiterpene synthases from sunflower capitate glandular trichomes

Background  

Sesquiterpene lactones are characteristic metabolites of Asteraceae (or Compositae) which often display potent bioactivities and are sequestered in specialized organs such as laticifers, resin ducts, and trichomes. For characterization of sunflower sesquiterpene synthases we employed a simple method to isolate pure trichomes from anther appendages which facilitated the identification of these genes and investigation of their enzymatic functions and expression patterns during trichome development.     

Anchoring a Plant Cytochrome P450 via PsaM to the Thylakoids in Synechococcus sp. PCC 7002: Evidence for Light-Driven Biosynthesis

Plants produce an immense variety of specialized metabolites, many of which are of high value as their bioactive properties make them useful as for instance pharmaceuticals. The compounds are often produced at low levels in the plant, and due to their complex structures, chemical synthesis may not be feasible. Here, we take advantage of the reducing equivalents generated in photosynthesis in developing an approach for producing plant bioactive natural compounds in a photosynthetic microorganism by functionally coupling a biosynthetic enzyme to photosystem I. This enables driving of the enzymatic reactions with electrons extracted from the photosynthetic electron transport chain. As a proof of concept, we have genetically fused the soluble catalytic domain of the cytochrome P450 CYP79A1, originating from the endoplasmic reticulum membranes of Sorghum bicolor, to a photosystem I subunit in the cyanobacterium Synechococcus sp. PCC 7002, thereby targeting it to the thylakoids. The engineered enzyme showed light-driven activity both in vivo and in vitro, demonstrating the possibility to achieve light-driven biosynthesis of high-value plant specialized metabolites in cyanobacteria.     

A comprehensive proteome map of glandular trichomes of hop (Humulus lupulus L.) female cones: Identification of biosynthetic pathways of the major terpenoid‐related compounds and possible transport proteins

Female flowers of hop (Humulus lupulus) are an essential source of terpenoid‐related compounds, which are mainly used as flavoring in the beer brewing process. The compounds involved are bitter acids, terpenophenolics, as well as mono‐ and sesquiterpenoids. In this work, we analyzed the proteome of purified glandular trichomes (lupulin glands) from female flowers, which produce and accumulate these compounds. An extensive 2D‐LC‐MS/MS analysis identified 1015 proteins. Of these, most correspond to housekeeping and primary metabolism‐related proteins, albeit predominantly including amino acid and lipid metabolism, which feeds the specialized (secondary) metabolism. Indeed, 75 proteins belong to the specialized metabolism. No less than 40 enzymes are involved in the synthesis of terpenoid‐derived compounds and 21 are predicted transporters, some of which might be involved in the transport of specialized metabolites. We discuss the possible routes involved in the intra‐ and intercellular translocation of terpenoids and their precursors. This comprehensive proteomic map of the glandular trichomes of hop female flowers represents a valuable resource to improve our knowledge on the function of glandular trichomes.     

Leaf hairs influence phytopathogenic fungus infection and confer an increased resistance when expressing a Trichoderma alpha-1,3-glucanase

The leaf surface of a very large number of plant species are covered by trichomes. Non-glandular trichomes are specialized unicellular or multicellular structures that occur in many different plant species and function in xenobiotic detoxification and protecting the plant against pest attack. By analysing the susceptibility of trichome mutants, evidence is provided that indicates the influence of leaf trichomes on foliar fungal infections in Arabidopsis thaliana, probably by facilitating the adhesion of the fungal spores/hyphae to the leaf surface. A decreased trichome number in the hairless Arabidopsis mutant gl1 enhances tolerance against the necrotrophic fungus Botrytis cinerea. By contrast, the try mutant shows an increased susceptibility to both fungal infection and accumulation. Trichome density does not influence infection by the soil-borne pathogen Rhizoctonia solani. In addition, the influence of trichomes on foliar infection is supported by targeting the high-level expression of the Trichoderma harzianum alpha-1,3-glucanase protein to the specialized cell structures. Trichome expression of this anti-fungal hydrolase shows a significant resistance to infection by the foliar pathogen Botrytis cinerea. Resistance to this fungus is not dependent on the constitutive induction of the salicylic or jasmonic defence signalling pathways, but the presence of the alpha-1,3-glucanase protein in trichomes.