An Integrated Analytical Approach Reveals Trichome Acylsugar Metabolite Diversity in the Wild Tomato Solanum pennellii

Abstract

Acylsugars constitute an abundant class of pest- and pathogen-protective Solanaceae family plant-specialized metabolites produced in secretory glandular trichomes. Solanum pennellii produces copious triacylated sucrose and glucose esters, and the core biosynthetic pathway producing these compounds was previously characterized. We performed untargeted metabolomic analysis of S. pennellii surface metabolites from accessions spanning the species range, which indicated geographic trends in the acylsugar profile and revealed two compound classes previously undescribed from this species, tetraacylglucoses and flavonoid aglycones. A combination of ultrahigh-performance liquid chromatography–high resolution mass spectrometry (UHPLC–HR-MS) and NMR spectroscopy identified variations in the number, length, and branching pattern of acyl chains, and the proportion of sugar cores in acylsugars among accessions. The new dimensions of acylsugar variation revealed by this analysis further indicate variation in the biosynthetic and degradative pathways responsible for acylsugar accumulation. These findings provide a starting point for deeper investigation of acylsugar biosynthesis, an understanding of which can be exploited through crop breeding or metabolic engineering strategies to improve the endogenous defenses of crop plants.

Natural variation in wild tomato trichomes; selecting metabolites that contribute to insect resistance using a random forest approach

“…These acylsugars consist of glucose-or sucrose moieties with acyl groups esterified to one-or more of its hydroxyl groups. The composition of acylsugars exudates can be highly diverse, as the complete blend is an assembly of acylsugars having different sugar moieties and varying acyl chain length-and positions [ 31 – 35 ]. Interestingly, insects appear to respond differently to particular acylsugar compositions, indicating that insect targeting is component specific [ 36 , 37 ].…”

It happened again: convergent evolution of acylglucose specialized metabolism in black nightshade and wild tomato

“…NMR-resolved structures of purified compounds are the gold standard for small molecule metabolites, but obtaining these data can be time-consuming. We sought to speed up the process by subjecting total extract or partially purified mixtures to 2D NMR analyses, taking advantage of previously developed acylsugar analysis methods ( 28, 29, 32 ) (Fig. 1 C ).…”

“…S3). We expect each acylglucose to resolve as two peaks corresponding to α and β anomers that interconvert, accounting for the presence of two peaks for each ( 29 ). The observation of additional peaks led to the hypothesis that four isomeric forms reflected different acyl chain branching patterns rather than differences in acyl group lengths or positions of esterification.…”

“…The presence of three distinct acylhexose classes – di- and triacylglucoses and triacylinositols – in S. nigrum presented a challenging case study for this integrative approach. We designed the pipeline to leverage the substantial chemical shift library assembled from acylsugar studies in other Solanaceous plants ( 10, 11, 13, 29, 34, 41 ).…”

“…As a result, while we have liquid chromatography–mass spectrometry (LC–MS) data for hundreds of structurally diverse acylsugars, only a subset have unambiguous structure annotations. For example, of more than 38 surveyed Solanaceae species that accumulate acylsugars, fewer than half have NMR structures elucidated for at least one acylsugar ( 14, 16, 21–26, 28, 29 ).…”