An RNA-Seq Analysis of Grape Plantlets Grown in vitro Reveals Different Responses to Blue, Green, Red LED Light, and White Fluorescent Light

Abstract

Using an RNA sequencing (RNA-seq) approach, we analyzed the differentially expressed genes (DEGs) and physiological behaviors of “Manicure Finger” grape plantlets grown in vitro under white, blue, green, and red light. A total of 670, 1601, and 746 DEGs were identified in plants exposed to blue, green, and red light, respectively, compared to the control (white light). By comparing the gene expression patterns with the growth and physiological responses of the grape plantlets, we were able to link the responses of the plants to light of different spectral wavelengths and the expression of particular sets of genes. Exposure to red and green light primarily triggered responses associated with the shade-avoidance syndrome (SAS), such as enhanced elongation of stems, reduced investment in leaf growth, and decreased chlorophyll levels accompanied by the expression of genes encoding histone H3, auxin repressed protein, xyloglucan endotransglycosylase/hydrolase, the ELIP protein, and microtubule proteins. Furthermore, specific light treatments were associated with the expression of a large number of genes, including those involved in the glucan metabolic pathway and the starch and sucrose metabolic pathways; these genes were up/down-regulated in ways that may explain the increase in the starch, sucrose, and total sugar contents in the plants. Moreover, the enhanced root growth and up-regulation of the expression of defense genes accompanied with SAS after exposure to red and green light may be related to the addition of 30 g/L sucrose to the culture medium of plantlets grown in vitro. In contrast, blue light induced the up-regulation of genes related to microtubules, serine carboxypeptidase, chlorophyll synthesis, and sugar degradation and the down-regulation of auxin-repressed protein as well as a large number of resistance-related genes that may promote leaf growth, improve chlorophyll synthesis and chloroplast development, increase the ratio of chlorophyll a (chla)/chlorophyll b (chlb), and decrease the ratio of carbohydrates to proteins in plants. Although exposure to red and green light seems to impose “shade stress” on the plantlets, growth under blue light is comparable to growth observed under white or broad-spectrum light.

Effects of Light Quality on Vegetative Cutting and In Vitro Propagation of Coleus (Plectranthus scutellarioides)

“…Blue light reportedly improved 5aminolevulinic acid synthesis in tobacco callus cells (Kamiya et al, 1983) and Chinese cabbage (Fan et al, 2013a), which is the key precursor in the chlorophyll biosynthetic pathway, followed by the conversion into protoporphyrin IX. Li et al (2017) reported blue light increased the expression of the genes encoding the heme-binding 2-like protein and chloroplast early light-induced protein, which may increase chlorophyll accumulation and promote chloroplast development in grape in vitro propagation. Once exposed to narrow-bandwidth B light, decreased L* values were detected in the coleus leaves, although they were not significant (Table 3), and similar results were reported that the wavelength from 400 to 500 nm produced darker, less chromatic pear fruits (Dussi et al, 1995).…”

“…4C), and Li et al (2010) reported similar results with cotton leaf tissue culture. Plant height and root growth were reduced in response to the blue light treatment in grape in vitro culture, possibly due to the blue light-induced down-regulation in the expression of the auxin-repressed protein gene, which made the endogenous auxin exceed the optimal level (Li et al, 2017). The compactness of seedlings could be a desirable characteristic so blue light treatment would be benefit for some specific plant production methods (Wollaeger and Runkle, 2014).…”

“…However, superbright blue light inhibited root formation in strawberry plantlets (Nhut et al, 2003). In grape in vitro culture, root development was reduced in response to blue light (Li et al, 2017). Light-emitting diodes (LEDs) make it possible to combine different wavelengths so that the customized mixture of lights may promote more desirable growth characteristics for species and cultivars (Batista et al, 2018;Massa et al, 2008).…”

Changes in the chlorophyll content of grape leaves could provide a physiological index for responses and adaptation to UV‐C radiation

“…For example, Chl a /Chl b levels increased in Hoe29, but decreased in Augster Weiss and Müller-Thurgau. This higher Chl a /Chl b ratio in Hoe29 further suggests that this genotype is well adapted to UV irradiation (Li et al 2017). In addition, the changes in Chl a levels were greater than were the change in Chl b , indicating that the overall changes in chlorophyll content in response to UV-C are mainly a consequence of Chl a production.…”

Physiological and Growth Response of Pepper (Capsicum annum L.) Seedlings to Supplementary Red/Blue Light Revealed through Transcriptomic Analysis

“…The LED-B (R:B = 8:1) increased plant height and stem diameter of the pepper plants more than the LED-A [10].With the progress of "next-generation" sequencing technology, transcriptome technology has been widely used to study the response of plants to the environment [11]. In grape plantlets under blue and red light treatments, the blue light induced the upregulation of genes related to microtubules, serine carboxypeptidase, and chlorophyll synthesis, but downregulated auxin-repressed protein and resistance-related genes [12], whereas red and green light promoted the expression of the auxin inhibitor protein gene, suggesting that the auxin concentrations are low in plants treated with red and green light, a condition that is suitable for plant stem and root length growth. Transcriptome sequencing of Saccharina japonica under blue light (notation by Swissprot, Nr, GO, KEGG, and COG databases) found that unigenes are putative BL photoreceptors; these genes are involved in processes of circadian rhythm, flavonoid biosynthesis, photo-reactivation, and photo-morphogenesis [13].Several authors have reported that the application of supplementary light improves the growth and development of vegetables, fruits, and ornamental plants under greenhouse conditions [14][15][16].…”