Saminathan Thangasamy, García Marleny, Ghimire Bandana, Lopez Carlos, Bodunrin Abiodun, Nimmakayala Padma, Abburi Venkata L, Levi Amnon, Balagurusamy Nagamani, Reddy Umesh K
Gus R. Douglass Institute and Department of Biology, West Virginia State University, Institute, WV, United States.
Laboratorio de Biorremediación, Facultad de Ciencias Biológicas, Universidad Autónoma de Coahuila, Torreón, Mexico.
Front Plant Sci. 2018 Jan 19;9:4. doi: 10.3389/fpls.2018.00004. eCollection 2018.
The plant microbiome is a key determinant of plant health and productivity, and changes in the plant microbiome can alter the tolerance to biotic and abiotic stresses and the quality of end produce. Little is known about the microbial diversity and its effect on carbohydrate metabolism in ripe fruits. In this study, we aimed to understand the diversity and function of microorganisms in relation to carbohydrate metabolism of ripe watermelon fruits. We used 16S metagenomics and RNAseq metatranscriptomics for analysis of red (PI459074, Congo, and SDRose) and yellow fruit-flesh cultivars (PI227202, PI435990, and JBush) of geographically and metabolically diverse watermelon cultivars. Metagenomics data showed that Proteobacteria were abundant in SDRose and PI227202, whereas Cyanobacteria were most abundant in Congo and PI4559074. In the case of metatranscriptome data, Proteobacteria was the most abundant in all cultivars. High expression of genes linked to infectious diseases and the expression of peptidoglycan hydrolases associated to pathogenicity of eukaryotic hosts was observed in SDRose, which could have resulted in low microbial diversity in this cultivar. The presence of GH28, associated with polygalacturonase activity in JBush and SDRose could be related to cell wall modifications including de-esterification and depolymerization, and consequent loss of galacturonic acid and neutral sugars. Moreover, based on the KEGG annotation of the expressed genes, nine α-galactosidase genes involved in key processes of galactosyl oligosaccharide metabolism, such as raffinose family were identified and galactose metabolism pathway was reconstructed. Results of this study underline the links between the host and fruit-associated microbiome in carbohydrate metabolism of the ripe fruits. The cultivar difference in watermelon reflects the quantum and diversity of the microbiome, which would benefit watermelon and other plant breeders aiming at the holobiont concept to incorporate associated microbiomes in breeding programs.
植物微生物群是植物健康和生产力的关键决定因素，植物微生物群的变化会改变植物对生物和非生物胁迫的耐受性以及最终产品的质量。关于成熟果实中微生物多样性及其对碳水化合物代谢的影响，人们了解甚少。在本研究中，我们旨在了解与成熟西瓜果实碳水化合物代谢相关的微生物的多样性和功能。我们使用16S宏基因组学和RNAseq宏转录组学分析了地理和代谢多样的西瓜品种的红肉（PI459074、刚果和SDRose）和黄肉品种（PI227202、PI435990和JBush）。宏基因组学数据显示，变形菌门在SDRose和PI227202中含量丰富，而蓝细菌在刚果和PI4559074中含量最高。在宏转录组数据方面，变形菌门在所有品种中含量最高。在SDRose中观察到与传染病相关的基因高表达以及与真核宿主致病性相关的肽聚糖水解酶的表达，这可能导致该品种微生物多样性较低。在JBush和SDRose中与多聚半乳糖醛酸酶活性相关的GH28的存在可能与细胞壁修饰有关，包括去酯化和解聚，以及随之而来的半乳糖醛酸和中性糖的损失。此外，基于表达基因的KEGG注释，鉴定了九个参与低聚半乳糖代谢关键过程（如棉子糖家族）的α-半乳糖苷酶基因，并重建了半乳糖代谢途径。本研究结果强调了成熟果实碳水化合物代谢中宿主与果实相关微生物群之间的联系。西瓜品种差异反映了微生物群的数量和多样性，这将有利于西瓜和其他旨在采用全生物概念将相关微生物群纳入育种计划的植物育种者。
