Abstract
Ginkgo (Ginkgo biloba L.) is a deciduous tree species with high timber, medicinal, ecological, ornamental, and scientific values, and is widely cultivated worldwide. However, for such an important tree species, the regulatory mechanisms involved in the photosynthesis of developing leaves remain largely unknown. Here, we observed variations in light response curves (LRCs) and photosynthetic parameters (photosynthetic capacity (Pnmax) and dark respiration rate (Rd)) of leaves across different developmental stages. We found the divergence in the abundance of compounds (such as 3-phospho-d-glyceroyl phosphate, sedoheptulose-1,7-bisphosphate, and malate) involved in photosynthetic carbon metabolism. Additionally, a co-expression network was constructed to reveal 242 correlations between transcription factors (TFs) and photosynthesis-related genes (p < 0.05, |r| > 0.8). We found that the genes involved in the photosynthetic light reaction pathway were regulated by multiple TFs, such as bHLH, WRKY, ARF, IDD, and TFIIIA. Our analysis allowed the identification of candidate genes that most likely regulate photosynthesis, primary carbon metabolism, and plant development and as such, provide a theoretical basis for improving the photosynthetic capacity and yield of ginkgo trees.
Highlights
Photosynthesis comprises temporal and spatial biochemical reactions that act in concert to convert light energy into chemical energy, representing the primary mechanism of dry matter production in plants [1]
Previous studies provided strong evidence that malate accumulation could significantly improve stomatal conductance and photosynthetic rate [43]. These results demonstrated that variation in photosynthetic capacity might be a strategy for maintaining the primary carbon metabolism to regulate growth and development [44]
The gene regulatory networks were generated by Cytoscape software (Version 3.7.1) [63]. This is the first report to evaluate the photosynthetic capacity of ginkgo leaves at different developmental stages
Summary
Photosynthesis comprises temporal and spatial biochemical reactions that act in concert to convert light energy into chemical energy, representing the primary mechanism of dry matter production in plants [1]. Photosynthesis improvement could increase carbon fixation and the production of biomaterials such as wood and fiber [3]. Carbon fixation is integrated over the entire growing season, so even small increases in the rate of photosynthesis can translate into yield increase [4]. The chlorophyll content, stomatal conductance, photosynthetic rate, carboxylation efficiency, related enzyme activities, and CO2 assimilation rate increase [7]. The light-saturated net photosynthetic rate on a leaf area basis peaks at or slightly before full leaf area expansion [8]. The photosynthetic capacity decreases with leaf senescence, which was mainly associated with the loss of ribulose-1,5-bisphosphate carboxylase [9]
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