Biology subjects

O'Maoileidigh, D. S.

Publications and source records attributed to O'Maoileidigh, D. S..

3 recordsLinked to original sources

bioRxiv2024

A promoter::luciferase reporter gene imaging toolkit in Kalanchoë laxiflora reveals molecular elements responsible for the circadian regulation of Crassulacean acid metabolism (CAM)

Crassulacean acid metabolism (CAM) plants perform primary atmospheric CO2 fixation at night, with timekeeping by the endogenous circadian clock. Understanding of circadian coordination of CAM remains limited to rhythmic post-translational regulation of phosphoenolpyruvate carboxylase (PPC) by a specific clock-controlled protein kinase, PPCK. Here, candidate promoter regions ([~]3000 bp) of CAM-associated genes from Kalanchoe laxiflora were coupled to a firefly luciferase reporter and stable transgenic lines of both K. laxiflora and C3 Arabidopsis thaliana were generated. In K. laxiflora, the CAM-associated GLUCOSE 6-PHOSPHATE/PHOSPHATE TRANSLOCATOR2 promoter (KlGPT2p) generated robust circadian rhythms of luciferase luminescence in constant conditions, with peak activity in leaf pair 3, where CAM-associated nocturnal CO2 fixation initiated during leaf development. KlGPT2p::LUC+ did not drive rhythms of luminescence in A. thaliana and the KlPPCK1 promoter produced no LUC+ signal in either species. Furthermore, the CHLOROPHYLL A/B BINDING PROTEIN2 promoter (KlCAB2p), a clock-controlled promoter that drives a gene involved in light-reactions of photosynthesis, drove robust rhythms in both K. laxiflora and A. thaliana. KlCAB2p circadian period changed during leaf development in K. laxiflora, revealing differing control by the core-clock during development. KlCAB2p peak activity shifted to dawn in A. thaliana relative to a dusk phased peak in CAM leaves of K. laxiflora, highlighting differences in the timing of outputs from the core clock between species. These findings establish a robust PROMOTER::LUC+ reporter system in a CAM plant and highlight divergent timing driving clock controlled promoters between species, and period lengthening with leaf age in Kalanchoe. One-sentence SummaryRobust circadian rhythms of firefly luciferase in the Crassulacean acid metabolism (CAM) model species Kalanchoe laxiflora were driven by both CAM and non-CAM gene promoters.

plant biology↗

bioRxiv2024

Measuring CO2 assimilation of Arabidopsis thaliana whole plants and seedlings

Photosynthesis is an essential process in plants that synthesizes sugars used for growth and development, highlighting the importance of establishing robust methods to monitor photosynthetic activity. Infrared gas analysis (IRGA) can be used to track photosynthetic rates by measuring the CO2 assimilation/release from a plant. Although much progress has been made in the development of IRGA technologies, challenges remain when using this technique on small herbaceous plants such as Arabidopsis thaliana. The use of whole plant chambers can overcome the difficulties associated with applying bulky leaf clamps to small delicate leaves, however this introduces the risk of soil-based microorganisms skewing gas exchange measurements. Here, we present a simple method to efficiently perform IRGA on A. thaliana plants using a whole plant chamber that removes soil-borne effects from the measurements. We show that this method can be used to detect subtle changes in photosynthetic rates measured at different times of day, under different growth conditions, and between wild-type and plants with deficiencies in the photosynthetic machinery. Furthermore, we show that this method can be used to detect changes in photosynthetic rates even at very young developmental stages such as 10 d-old seedlings. This method contributes to the array of techniques currently used to perform IRGA on A. thaliana and can allow for the monitoring of photosynthetic rates of whole plants from young ages.

plant biology↗

bioRxiv2023

AGAMOUS mediates timing of guard cell formation during gynoecium development

In Arabidopsis thaliana, stomata are composed of two guard cells that control the aperture of a central pore to facilitate gas exchange between the plant and its environment, which is particularly important during photosynthesis. Although leaves are the primary photosynthetic organs of higher plants, floral organs are also photosynthetically active. In the Brassicaceae, evidence suggests that silique photosynthesis is important for optimal seed oil content. A group of transcription factors containing MADS DNA binding domains is necessary and sufficient to confer floral organ identity. Elegant models, such as the ABCE model of flower development and the floral quartet model, have been instrumental in describing the molecular mechanisms by which these floral organ identity proteins govern flower development. However, we lack a complete understanding of how the floral organ identity genes interact with the underlying leaf development program. Here, we show that the MADS domain transcription factor AGAMOUS (AG) represses stomatal development on the gynoecial valves, so that maturation of stomatal complexes coincides with fertilization. We present evidence that this regulation by AG is mediated by direct transcriptional repression of the master regulator of the stomatal lineage, MUTE, and that this interaction is conserved among the Brassicaceae. This work extends on our understanding of the mechanisms underlying floral organ formation and provides a framework to decipher the mechanisms that control floral organ photosynthesis.

plant biology↗