Modelling of plant circadian clock for characterizing hypocotyl growth under different light quality conditions

Abstract

To meet the ever-increasing global food demand, the food production rate needs to be increased significantly in the near future. Speed breeding is considered as a promising agricultural technology solution to achieve the zero-hunger vision as specified in the United Nations Sustainable Development Goal 2. In speed breeding, the photoperiod of the artificial light has been manipulated to enhance crop productivity. In particular, regulating the photoperiod of different light qualities rather than solely white light can further improve speed breading. However, identifying the optimal light quality and the associated photoperiod simultaneously remains a challenging open problem due to complex interactions between multiple photoreceptors and proteins controlling plant growth. To tackle this, we develop a first comprehensive model describing the profound effect of multiple light qualities with different photoperiods on plant growth (i.e., hypocotyl growth). The model predicts that hypocotyls elongated more under red light compared to both red and blue light. Drawing similar findings from previous related studies, we propose that this might result from the competitive binding of red and blue light receptors, primarily Phytochrome B (phyB) and Cryptochrome 1 (cry1) for the core photomorphogenic regulator, CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). This prediction is validated through an experimental study on Arabidopsis thaliana. Our work proposes a potential molecular mechanism underlying plant growth under different light qualities and ultimately suggests an optimal breeding protocol that takes into account light quality.

Red Light Resets the Expression Pattern, Phase, and Period of the Circadian Clock in Plants: A Computational Approach

“…CCA1 gene expression has been found to be induced by light signal and may have different profiles in different Arabidopsis lines [ 40 , 49 ]. Moreover, TOC1 and ELF4 have been reported to act negatively and positively, respectively, on CCA1 / LHY expression under red-light exposure [ 40 , 46 ]. Here, we examined and predicted the effect of a 1 h red-light pulse on CL transcriptional levels in WT, TOC1-OX, the toc1 mutant, ELF4-OX, and the elf4 mutant.…”

“…Instead of white-light input in the De Caluwé model [ 10 ], we replenished red-light cues to the main clock. According to experiments, red light regulates circadian clock components by affecting the rates of transcription, translation, and post-translation modification [ 43 , 44 , 45 , 46 ]. Protein degradation is modeled based on the fact that phyB regulates the circadian clock components through direct protein–protein interactions.…”

An Extended Plant Circadian Clock Model for Characterising Flowering Time under Different Light Quality Conditions

“…In our previous work [10], we modelled the effect of various light qualities on the hypocotyl length, which is the first stage of plant growth. In the second stage, flowering will happen and in the final step, ripening will happen, which will ultimately determine the yield.…”

“…In the second stage, flowering will happen and in the final step, ripening will happen, which will ultimately determine the yield. As such, extending the model developed in [10] by considering flowering time as one of the outputs would be the next logical step. In [11], the authors have developed a mathematical model relating PCS to flowering time that solely considers white light.…”

“…In [11], the authors have developed a mathematical model relating PCS to flowering time that solely considers white light. In this work, we modify that model by taking into account the effect of blue, red, and mixed lights and incorporate it into our previously developed model [10], which distinguishes this current work from that of [11]. The inclusion of flowering time to the existing hypocotyl length would thereby provide more flexibility in manipulating lighting conditions for speed breeding purpose.…”