RNA-Seq Analysis Reveals Differential Responses of Potato (Solanum tuberosum L.) Plantlets Cultured in vitro to Red, Blue, Green, and White Light-emitting Diodes (LEDs)

Differentially expressed genes (DEGs), morphological changes, and leaf ultrastructure alterations of "Zhong Shu 3" potato (Solanum tuberosum L.) plantlets in vitro cultured under red (R), blue (B), green (G), or white (W) LEDs were analyzed using RNA sequencing (RNA-Seq) method. In total, 2160, 774, and 1335 DEGs were identified in plantlets that received R, B, and G LEDs, respectively, compared to W LEDs (the control). Higher expression of expasin, xyloglucan glycosyltransferase, actin, and tubulin genes were associated with the largest leaf area under B and W LEDs. Neatly arranged spongy and palisade cells were observed in plantlets exposed to R LEDs, accompanied by upregulated expression of all the DEGs enriched for "anatomical structure development" and "anatomical structure arrangement" biological processes. Well-developed chloroplasts with developed inner membranes in plantlets under B LEDs were associated with the upregulation of most DEGs enriched for gene ontology (GO) terms of the chloroplast and chloroplast membrane systems. In addition, different light qualities induced different gene expression patterns, many of which were involved in metabolic pathways, such as the "porphyrin and chlorophyll metabolism pathway Ko00860." Regulation of these genes might explain the higher or lower contents of photosynthetic pigments. Although R and G LEDs triggered shade stress in potato plantlets in vitro, the health index of plantlets grown under B LEDs was higher than that grown under W LEDs. Our results provide insights into the responses of potato plantlets to different light qualities at the transcriptomic level and may contribute to the improvement of potato plantlet in vitro propagation from light spectrum aspects.