Biology subjects

Macknight, R. C.

Publications and source records attributed to Macknight, R. C..

3 recordsLinked to original sources

bioRxiv2025

FLOWERING LOCUS T genes MtFTb1 and MtFTb2 act redundantly to promote flowering under long days in Medicago truncatula

Flowering time is a crucial agronomic trait affecting yield and plant performance in different climates and photoperiods. While the molecular pathways regulating photoperiodic flowering are well-characterised in Arabidopsis and cereals, they remain poorly understood in many other groups of plants. FLOWERING LOCUS T (FT) genes are key components regulating the transition from vegetative to reproductive stages. In the legume Medicago truncatula, a forage crop, six FT orthologs are present. To date, only the role of MtFTa1 has been described, promoting flowering after prolonged exposure to cold (vernalization), while the other five remains unclear. Here we show that MtFTb1 and MtFTb2 together are essential for flowering under long-day (LD) photoperiods. Using CRISPR/Cas9, we generated Mtftb1 single mutants and Mtftb1/2 double mutants. MtFTb1 and MtFTb2 genes act redundantly and are required to up-regulate MtFTa1 under vernalised LD conditions. While Mtftb1 mutants flower normally under short-day (SD) and LD conditions, Mtftb1/2 mutants are delayed specifically under LD but retain a vernalization response. Transcriptomic analysis of wild-type and Mtftb1/2 mutants shows MtFTb1/2 are essential for MADS-box gene upregulation and modulate known and candidate flowering regulators under LD. These findings advance our understanding of flowering time control in legumes and may inform strategies to improve forage crop productivity. HighlightMtFTb1 and MtFTb2 genes control flowering under long days in Medicago truncatula, revealing clade-specific functions of MtFT genes and providing novel insights into the environmental regulation of flowering time in legumes.

plant biology↗

bioRxiv2022

The 5'-3' exoribonuclease XRN4 modulates the plant circadian network in Arabidopsis

Circadian rhythms enable organisms to anticipate and adjust their physiology to periodic environmental changes. These rhythms are controlled by biological clocks that consist of a set of clock genes that regulate each other expression. Circadian oscillations in mRNA levels require regulation of mRNA production and degradation. While transcription factors controlling clock function have been well characterized from cyanobacteria to humans, the role of factors controlling mRNA decay is largely unknown. Here, we show that mutations in XRN4, the central component of the 5-3 mRNA decay pathway, alter clock function in Arabidopsis. We found that xrn4 mutants display long period phenotypes for clock gene expression and for the rhythm of leaf movement. These circadian defects were associated with changes in the circadian phases, but not overall mRNA levels, of several core clock genes. We then used non-invasive transcriptome-wide mRNA stability analysis to identify genes and pathways regulated by XRN4. Among genes affected in the xrn4 mutant at the transcriptional and post-transcriptional level, we found an enrichment in genes involved in auxin, ethylene, ABA signaling, and also circadian rhythmicity, although no significant effects were observed for canonical core-clock genes. Strikingly, the mRNAs of several clock regulated BBX genes were stabilized in xrn4 mutants. Some of these BBX genes are auxiliary factors controlling the pace of the clock and are candidates to mediate XRN4 effects on circadian period. Our results establish that, in Arabidopsis, the control of 5-3 mRNA decay by XRN4 constitutes a novel post-transcriptional regulatory layer of the circadian gene network.

plant biology↗

bioRxiv2021

Transcriptomic Insights into the Responses in Leaves Storing Lipid Organelles under Different Irradiances

To increase the nutritional value of forage, transgenic ryegrass known as High Metabolizable Energy (HME) were previously generated that co-express cysteine-oleosin and diacylglycerol O-acyltransferase. HME not only accumulate lipids in the leaf but also has elevated CO2 assimilation and increased biomass. Shading is one of the most influencing factors for ryegrass growth environments particularly in swards. The aim of this study, therefore, was to determine the influence of irradiance levels on photosynthesis and gene expression in the HME leaves when compared with their corresponding non-transformant (NT). Under low light (150-250 {micro}mol m-2 s-1) and standard light (600-1000 {micro}mol m-2 s-1), the HME accumulated more lipid than NT. The previously reported elevated photosynthesis and increased biomass was observed when the HME were grown under standard light but not under low light. Under both light conditions, compared to NT, the HME had upregulated a number of transcripts involved in lipid metabolism, light capturing, photosynthesis, and sugar signalling network while downregulated genes participated in sugar and fructan biosynthesis. We further discuss how the HME differentially manipulated several genes other metabolic pathways including maintenance of redox homeostasis. Combined, the data suggests that the increased photosynthesis capacity in the HME likely corresponds to an increase of micro-lipid sink strength; these are influenced by available light energy and may be related to diffusional and biochemical activities of stomata. Overall, this work provides a clearly understanding of the changes in molecular and biochemical mechanisms underlying the carbon storing as leaf lipid sink of the HME ryegrass. One sentence summaryShading led to increase leaf lipid accumulation but limit the greater photosynthesis trait of high lipid ryegrass which may be related to limitation of biochemical activities of stomata.

molecular biology↗