Project description:Duckweed-associated plant growth-promoting bacteria (PGPB) have attracted considerable attention for enhancing duckweed biomass production; however, the mechanisms underlying strain-specific plant growth promotion remain largely unknown. Here, we compared the effects of two duckweed-associated bacterial strains, Terrimicrobium sp. PS02 and Aeromicrobium sp. PS05, on the growth, biomass composition, colonization behavior, and transcriptomic responses of Spirodela polyrhiza. While both strains enhanced duckweed biomass, PS02 yielded a 1.2-fold increase, whereas PS05 induced a statistically significant increase (1.4-fold) compared with the uninoculated control. Markedly, PS05 established approximately one order of magnitude higher bacterial populations than PS02 and formed dense extracellular polymeric substance (EPS)-mediated microcolonies on duckweed surfaces. Transcriptome analysis revealed that PS05 induced 1,108 differentially expressed genes, compared with 454 genes for PS02, indicating substantially greater host transcriptomic reprogramming. Functional enrichment analyses demonstrated that PS05 preferentially regulated carbohydrate biosynthesis and central carbon metabolism. Consistently, both transcriptomic and RT-qPCR analyses showed up-regulation of key genes involved in starch biosynthesis and carbon allocation, resulting in significantly enhanced starch accumulation and turion formation without reducing protein or photosynthetic pigment content. This study provides the first integrated evidence linking bacterial colonization strategy, host transcriptomic regulation, carbon allocation, and biomass production in duckweed, thereby establishing a mechanistic basis for engineering high-performance duckweed–microbiome systems for sustainable biomass production.
Project description:The greater duckweed (Spirodela polyrhiza 7498) exhibits trophic diversity (photoautotrophic, heterotrophic, photoheterotrophic, and mixotrophic growth) depending on the availability of exogenous organic carbon sources and light. Here, we show that the ability to transition between various trophic growth conditions is an advantageous trait, providing great phenotypic plasticity and metabolic flexibility in S. polyrhiza 7498. By comparing S. polyrhiza 7498 growth characteristics, metabolic acclimation, and cellular ultrastructure across these trophic modes, we show that mixotrophy decreases photosynthetic performance and relieves the CO2 limitation of photosynthesis by enhancing the CO2 supply through the active respiration pathway. Proteomic and metabolomic analyses corroborated that S. polyrhiza 7498 increases its intracellular CO2 and decreases reactive oxygen species undermixotrophic and heterotrophic conditions, which substantially suppressed the wasteful photorespiration and oxidative-damage pathways. As a consequence, mixotrophy resulted in a higher biomass yield than the sum of photoautotrophy and heterotrophy.Our work provides a basis for using trophic transitions in S. polyrhiza 7498 for the enhanced accumulation of value-added products.
2023-02-27 | PXD040410 |
Project description:Isoform sequencing of Spirodela polyrhiza 7498
Project description:Duckweeds are a monophyletic group of rapidly reproducing aquatic monocots in the Lemnaceae family. Spirodela polyrhiza, the Greater Duckweed, has the largest body plan yet the smallest genome size in the family (1C = 150 Mb). Given their clonal, exponentially fast reproduction, a key question is whether genome structure is conserved across the species in the absence of meiotic recombination. We generated a highly contiguous, chromosome-scale assembly of Spirodela polyrhiza line Sp7498 using Oxford Nanopore plus Hi-C scaffolding (Sp7498_HiC) that is highly syntenic with a related line (Sp9509). Both the Sp7498_HiC and Sp9509 genome assemblies reveal large chromosomal misorientations in a recent PacBio assembly of Sp7498, highlighting the necessity of orthogonal long-range scaffolding techniques like Hi-C and BioNano optical mapping. Proteome analysis of Sp7498 verified the expression of nearly 2,250 proteins and revealed a high level of proteins involved in photosynthesis and carbohydrate metabolism among other functions. In addition, a strong increase in chloroplast proteins was observed that correlated to chloroplast density. This Sp7498_HiC genome was generated cheaply and quickly with a single Oxford Nanopore MinION flow cell and one Hi-C library in a classroom setting. Combining these data with a mass spectrometry-generated proteome, demonstrates that duckweed is a model for genomics- and proteomics-based education.