Biology subjects

Müller, L. M.

Publications and source records attributed to Müller, L. M..

4 recordsLinked to original sources

bioRxiv2026

Phasor EO-FLIM: Lifetime imaging with picosecond noise and 500 Hz frame rate

Fluorescence lifetime microscopy is limited by photon throughput, constraining the speed and dynamic range of biological measurements. We demonstrate a compact optical module and fast phasor acquisition methods to image multi-exponential lifetimes at 500 Hz in vivo and with over 1010 photons per second in static tissues. Action potentials are captured in phasor plots, and lifetime contrast is revealed from autofluorescence and wheat germ agglutinin stain with 20 picosecond pixel noise.

bioengineering↗

bioRxiv2025

Mutation of M. truncatula SOBIR1 affects rhizobial specificity and arbuscular mycorrhizal colonization

Legume plants form symbiotic interactions with bacteria (rhizobia sp.) to obtain fixed nitrogen and arbuscular mycorrhizal fungi to obtain phosphorus and other nutrients. These interactions require the plant to distinguish beneficial from pathogenic organisms and trigger the plants innate immune system. We identified mutants in the Medicago truncatula SOBIR1 gene, known to be involved in innate immune response in multiple plants. We examined nodulation with multiple strains and species of Sinorhizobium and examined mycorrhizal interactions with the arbuscular mycorrhizal fungus Glomus versiforme (recently renamed Diversispora epigaea). Plants containing mutations in SOBIR1 exhibit normal nodulation with strains of S. meliloti, but fewer nodules when inoculated with S. medicae strains. The S. medicae nodules show evidence of accumulation of polyphenolic compounds, and abnormal arrangement of the rhizobia within the nodules. In contrast, when inoculated with Glomus versiforme. M. truncatula sobir1 mutant plants have increased mycorrhizal colonization and arbuscule number compared to the wild type. We localized a tagged SOBIR1 protein to the periarbuscular membrane interface. Together the data suggest the immune kinase SOBIR1 is involved in both nodulation and mycorrhizal interactions, but the effects of mutation differ.

plant biology↗

bioRxiv2023

TML1 AND TML2 SYNERGISTICALLY REGULATE NODULATION BUT NOT ARBUSCULAR MYCORRHIZA IN MEDICAGO TRUNCATULA

Two symbiotic processes, nodulation and arbuscular mycorrhiza, are primarily controlled by the plants need for nitrogen (N) and phosphorus (P), respectively. Autoregulation of Nodulation (AON) and Autoregulation of Mycorrhization (AOM) both negatively regulate their respective processes and share multiple components - plants that make too many nodules usually have higher AM fungal root colonization. The protein TML (TOO MUCH LOVE) was shown to function in roots to maintain susceptibly to rhizobial infection under low N conditions and control nodule number through AON in Lotus japonicus. M. truncatula has two sequence homologs: MtTML1 and MtTML2. We report the generation of stable single and double mutants harboring multiple allelic variations in MtTML1 and MtTML2 using CRISPR-Cas9 targeted mutagenesis and screening of a transposon mutagenesis library. Plants containing single mutations in MtTML1 or MtTML2 produced 2-3 times the nodules of wild-type plants whereas plants containing mutations in both genes displayed a synergistic effect, forming 20x more nodules compared to wild type plants. Examination of expression and heterozygote effects suggest genetic compensation may play a role in the observed synergy. Plants with mutations in both TMLs only showed mild increases in AM fungal root colonization at later timepoints in our experiments, suggesting these genes may also play a minor role in AM symbiosis regulation. The mutants created will be useful tools to dissect the mechanism of synergistic action of MtTML1 and MtTML2 in M. truncatula symbiosis with beneficial microbes.

molecular biology↗

bioRxiv2020

Constitutive overexpression of RAM1 increases arbuscule density during arbuscular mycorrhizal symbiosis in Brachypodium distachyon

Arbuscular mycorrhizal (AM) symbiosis is a mutually beneficial association of plants and fungi of the sub-phylum Glomeromycotina. The endosymbiotic AM fungi colonize the inner cortical cells of the roots, where they form branched hyphae called arbuscules that function in nutrient exchange with the plant. To support arbuscule development and subsequently bidirectional nutrient exchange, the root cortical cells undergo substantial transcriptional re-programming. REDUCED ARBUSCULAR MYCORRHIZA 1 (RAM1), studied in several dicot plant species, is a major regulator of this cortical cell transcriptional program. Here, we generated ram1 mutants and RAM1 overexpressors in a monocot, Brachypodium distachyon. The AM phenotypes of two ram1 lines revealed that RAM1 is only partly required to enable arbuscule development in B. distachyon. Transgenic lines constitutively overexpressing BdRAM1 showed constitutive expression of AM-inducible genes even in the shoots. Following inoculation with AM fungi, BdRAM1-overexpressing roots showed higher arbuscule densities relative to controls, indicating the potential to manipulate the relative proportion of symbiotic interfaces via modulation of RAM1. However, the overexpressors also show altered expression of hormone biosynthesis genes and aberrant growth patterns including stunted bushy shoots and poor seed set. While these phenotypes possibly provide additional clues about BdRAM1s scope of influence, they also indicate that directed approaches to increase the density of symbiotic interfaces will require a more focused, potentially cell-type specific manipulation of transcription factor gene expression.

plant biology↗