Phenotypic and transcriptional features of the Araliaceae species under distinct light environments

Elucidating how the plant species respond to variable light conditions is essential to understand the ecological adaptation to heterogeneous environments. Plant performance and gene regulatory network underpinning the adaptation have been well-documented in sun-grown species. In this study, we surveyed phenotypic and transcriptomic features of four shade-grown and one sun-grown woody species of the family Araliaceae under distinct light conditions. Our phenotypic comparisons demonstrate that the four shade-grown species possess lower light saturation point and higher assimilation ability of the net photosynthetic rate compared to the sun-grown species. In particular, the four shade-grown species maintain similar photosynthesis efficiency in both highlight and lowlight conditions. However, a significantly decreased photosynthesis rate was observed under lowlight condition of the sun-grown species compared to highlight condition. In addition, our leaf anatomical analyses reveal that while all the five species show different anatomical structures under distinct light conditions, the shade-grown species possess lower degree of phenotypic plasticity relative the sun-grown species. Further comparisons of the transcriptome profiling show that all the five species exhibit gene expression divergence among different light conditions. The differentially expressed genes identified in the five species are functionally related to photosynthesis, secondary metabolites and other basic metabolisms. More importantly, differential regulation of the photosynthesis- and photomorphogenesis-related genes are potentially correlated with the phenotypic responses to distinct light conditions of the five species. Our study provides new insights on how the sun- and shade-grown woody species respond to shade and sunlight environments.