Biology subjects

Koo, A. J.

Publications and source records attributed to Koo, A. J..

3 recordsLinked to original sources

bioRxiv2025

Persistent fatty acid catabolism during plant oil synthesis

Plant lipids are an essential energy source for diets and are a sustainable alternative to petroleum-based fuels and feed stocks. Fatty acid breakdown during seed germination is crucial for seedling establishment but unexpected during seed filling. Here, we demonstrate that the simultaneous biosynthesis and degradation of fatty acids begins early and continues across all phases of oil filling and throughout the photoperiod. Tests in camelina, rapeseed and engineered high-oil tobacco line confirmed that concomitant synthesis and breakdown in oil-producing tissues over development is the rule rather than the exception. We show that transgenics, designed for significantly higher fatty acid biosynthesis, fail to achieve a proportional increase in storage lipid levels due to increasing degradation, potentially explaining the underperformance of engineered lines compared to expectations.

plant biology↗

bioRxiv2023

Comparative omics reveals unanticipated metabolic rearrangements in a high-oil mutant of plastid acetyl-CoA carboxylase

Heteromeric acetyl-CoA carboxylase (ACCase) catalyzes the ATP-dependent carboxylation of acetyl-CoA to produce malonyl-CoA, the committed step for de novo fatty acid synthesis. In plants, ACCase activity is controlled at multiple levels, including negative regulation by biotin attachment domain-containing (BADC) proteins, of which the badc1/3 double mutant leads to increased seed triacylglycerol accumulation. Unexpectedly, the Arabidopsis badc1/3 mutant also accumulates more protein. The metabolic consequences from both higher oil and protein was investigated in developing badc1/3 seed using global transcriptomics, translatomics, proteomics, and metabolomics. Changes include: reduced plastid pyruvate dehydrogenase; increased acetyl-CoA synthetase; increased storage and lipid-droplet packaging proteins; increased lipases; and increased {beta}-oxidation fatty acid catabolism. We present a model of how Arabidopsis adapted to deregulated ACCase, limiting total oil accumulation, and altering flux through pathways of carbon accumulation that presents possible targets for future bioengineering of valuable seed storage reserves.

plant biology↗

bioRxiv2019

A light-dependent molecular link between competition cues and defense responses in plants

One of the principal internal signals controlling plant growth and defense is jasmonate (JA), a potent growth inhibitor that is simultaneously a central regulator of plant immunity to herbivores and pathogens. When shade-intolerant plants perceive the proximity of competitors using the photoreceptor phytochrome B (phyB), they accelerate growth and down-regulate JA responses. However, the mechanisms by which photoreceptors relay light cues to the JA signaling pathway are not understood. Here we identify a sulfotransferase (ST2a) that is strongly up-regulated by plant proximity perceived by phyB via the phyB-Phytochrome Interacting Factor (PIF) signaling module. By catalyzing the formation of a sulfated JA derivative, ST2a acts to degrade bioactive forms of JA and represents a direct molecular link between photoreceptors and hormone signaling in plants. The enzyme provides a molecular mechanism for prioritizing shade avoidance over defense under close plant competition.

plant biology↗