Gene Expression Characteristics for Photosynthesis During Somatic Embryo Seed-Like Germination of Rosa hybrida

Photosynthesis is a key energy and matter source for plant growth, with its regulatory mechanisms long being a research focus. However, there are currently few reports on the molecular mechanisms of photosynthesis during plantlet regeneration. In this study, the single-piece cotyledonary somatic embryos (SPC explants, served as the control sample for transcriptome sequencing) of Rosa hybrida "J.F. Kennedy" and its regenerated material, the regenerated seedlings with a single bud along the longitudinal axis (RSLA seedlings, a classic regenerated material for seed-like germination), were collected for transcriptome sequencing and determination of physiological and biochemical indicators. Transcriptome data analysis revealed that almost all genes related to chloroplast development and chlorophyll biosynthesis were upregulated in RSLA seedlings, and the contents of chlorophyll a and b in the RSLA seedlings were significantly higher than those in the SPC explants. Additionally, all 26 light reaction-related genes were upregulated during plantlet regeneration of rose somatic embryos. Key genes AGPase, SS, and SPS involved in photosynthetic product synthesis in the carbon reaction showed differential expression between the two materials. RSLA seedlings had significantly higher starch content than SPC explants, while sucrose content showed the opposite trend. In summary, during rose somatic embryo plantlet regeneration, most photosynthesis-related genes were upregulated in regenerated RSLA seedlings, indicating high activation of chlorophyll (light energy capture substance) and starch (energy storage substance) synthesis pathways. These results filled the research gap in the photosynthetic mechanism of rose somatic embryo seed-like germination and plantlet regeneration at transcriptomic and physiological-biochemical levels, providing a reference for photosynthetic regulation in in vitro plantlet regeneration.