Tailoring the light: multi-omic insights into how light quality and quantity shape kale cultivars

Abstract

This article comments on:

Scandola S, Grubb LE, Castillo B, Iliscupidez L, Kennedy C, Boyce N, Talasila M, Uhrig RG. 2026. Shaping kale morphology and physiology using precision LED light recipes. Journal of Experimental Botany 77, 5206–5224. https://doi.org/10.1093/jxb/erag163

This article comments on:

Scandola S, Grubb LE, Castillo B, Iliscupidez L, Kennedy C, Boyce N, Talasila M, Uhrig RG. 2026. Shaping kale morphology and physiology using precision LED light recipes. Journal of Experimental Botany 77, 5206–5224. https://doi.org/10.1093/jxb/erag163

Plant morphology and physiology are determined by a combination of internal circadian rhythms and external light quality. While the responses to light are generally conserved across varieties, recent evidence suggests significant morphological and metabolic differences between related cultivars, suggesting a need for cultivar-specific light optimization. Leveraging high-resolution proteomics and metabolomics, Scandola et al. (2026) investigated diel proteome and metabolome changes in two kale cultivars under various LED-driven light intensities and spectra, respectively. Their findings provide critical insights for optimizing harvest timing and light recipes to maximize specific traits of interest.

The quest for an optimal light recipe

As indoor farming gains momentum, the optimization of ‘light recipes’, the precise titration of light intensity and spectrum, has become a pivotal area of research. Tailoring these recipes allows growers to maximize biomass or the production of beneficial metabolites (Ouzounis et al., 2015). This optimization is complex because plant architecture is governed by light-intensity-driven photosynthesis and spectrum-sensing photoreceptors. In the model plant Arabidopsis thaliana, for instance, the phytochrome system mediates the shade avoidance syndrome (SAS), where a low red to far-red (R/FR) ratio signals the presence of a competing canopy, triggering rapid elongation (Pierik and de Wit, 2014). While the reduction in blue light can also induce the SAS in Arabidopsis (de Wit et al., 2016), growth under blue light alone does not induce such a response (Spaninks et al., 2020). Unlike Arabidopsis, Chinese kale seedlings show hypocotyl elongation under both red-only and blue-only light (Chen et al., 2021). Such discrepancies underscore that light spectrum responses are species specific, necessitating tailored investigations for different crop species.

Commercial kale (Brassica oleracea var. sabellica) exhibits various morphological adaptations across cultivars, which have previously been investigated for a number of commercial kale cultivars (Scandola et al., 2023). However, the molecular mechanisms driving their adaptation to light qualities remained unexplored. Scandola et al. (2026) focused on two genetically related but morphologically divergent cultivars, Dwarf Curled Scotch and Red Scarlet, and employed a high-resolution, library-free BoxCarDIA-based proteomic approach (Mehta et al., 2022) integrated with metabolomics. By sampling at the end of the day (Zeitgeber time, ZT11, i.e. the time before lights turn OFF) and the end of the night (ZT23, i.e. the time before the lights turn ON), they capture the diel fluctuations of the proteome and metabolome, providing a temporal map of how light conditions influence horticultural traits, such as glucosinolate, amino acid, carotenoid, and antioxidant compound production.

Cultivar-specific morphological differences and associated proteome and metabolome changes

Scandola et al. (2026) found striking divergence in adaptation strategies between the two cultivars. While Dwarf Curled Scotch was responsive to both light intensity and spectrum, Red Scarlet responded primarily to light intensity in terms of biomass (Fig. 1). Notably, Dwarf Curled Scotch exhibited an SAS-like morphological response under low R/FR and low R/B conditions, an adaptation entirely absent in Red Scarlet. This morphological shift was mirrored at the molecular level: in Dwarf Curled Scotch, proteins associated with cell wall remodelling, such as XTH proteins, were down-regulated under balanced light compared with low R/FR at ZT11. This suggests that the light spectrum does not just change the morphology of the plant, but actively modulates protein abundance in a time-of-day-dependent manner.

Fig. 1.

Comparative light intensity and spectral responses of two kale cultivars. Scandola et al. (2026) investigated the light intensity and spectral responses of two kale cultivars, Dwarf Curled Scotch (left side) and Red Scarlet (right side). The width of the yellow arrow indicates the various intensities of photosynthetic photon flux density (PPFD), and the colour of the purple and dark red arrows indicates the various ratios of red–blue (R/B) light and red–far-red (R/FR) light, respectively. While Dwarf Curled Scotch shows both light spectrum and light intensity response, Red Scarlet shows a relatively more pronounced light intensity response than a light spectrum response. Commercially valuable metabolites such as glucosinolates, ascorbic acids, carotenoids, and anthocyanins show a distinct accumulation pattern in certain light qualities. Cell wall-associated proteins such as xyloglucan endotransglucosylases/hydrolases (XTHs) are also more abundant in Dwarf Curled Scotch under the low R/B and low R/FR conditions, and in Red Scarlet under the low PPFD condition.

Beyond investigating plant architecture, the study provides critical insights into the production of high-value metabolites. Both cultivars increased the levels of glucosinolates in response to higher light intensity, yet they did so through different pathways: Red Scarlet by down-regulating catabolism and Dwarf Curled Scotch by up-regulating biosynthesis. Similarly, their antioxidant profiles differed: Red Scarlet had increased carotenoid and anthocyanin accumulation under specific spectral conditions, whereas Dwarf Curled Scotch showed increased ascorbic acid (vitamin C) production, particularly at ZT11 under higher photosynthetic photon flux density (PPFD).

Diel post-translational modifications, and the timing of light treatment

The work by Scandola et al. (2026) provides a high-resolution snapshot of the proteome and metabolome as affected by the light treatment, and opens the door to deeper questions regarding the regulation of these processes. Given that the circadian clock governs 80–90% of gene expression in plants (Millar, 2016), the focus has historically been on transcriptomics. However, as this study demonstrates, the time lag between transcript elevation and protein abundance makes direct proteomic analysis indispensable for agricultural optimization (Mehta et al., 2021). To unlock the potential of precision lighting, the next frontier must move beyond protein abundance toward protein function. Post-translational modifications (PTMs), such as phosphorylation and lysine acetylation, are highly sensitive to both light conditions and diurnal cycles (Uhrig et al., 2019; Giese et al., 2023; Eirich et al., 2024). Investigating PTMs in agronomical crops would provide a better understanding of enzyme activity and metabolic flux, moving us from a static map of ‘what is present’ to a dynamic understanding of ‘what is active’, and metabolite abundance, especially that of central metabolites, is also changing during the diurnal cycle (Cervela-Cardona et al., 2021).

Furthermore, we should consider that the ‘optimal light recipe’ may not be a constant state, but a temporal sequence. Recent findings in lettuce suggest that the timing of specific spectral inputs, such as adding FR light during the seedling stage and reducing it later, can significantly boost final biomass (Levine et al., 2026). This suggests that the future of indoor farming lies in ‘dynamic lighting’, where the spectrum and intensity evolve in tandem with the developmental stage of the plant and its internal clock. By integrating the diel insights provided by Scandola et al. (2026) with stage-specific lighting strategies and timing of the treatment, we can move toward a truly optimized approach of kale crop production in indoor farming.