Interspecific variance of molecular response to external pH conditions in two Rhododendron species

Soil acidification has been widely recognized as a server environmental issue. Acid soil causes hazards to plant species’ development, growth and also the yield of crop through the world. Rhododendron species have been demonstrated to prefer to grow in acid soil. However, the molecular-response mechanism of Rhododendron seedlings and their interspecific variance to different pH conditions remains unclear. Herein, we compared the response of R. decorum and R. griersonianum to different pH treatments through physiological indicators, transcriptome analysis, and weighted gene co-expression network analysis. We found that the physiological and biochemical traits and DEG numbers indicted that the narrow-ranging species R. griersonianum was more sensitive to pH conditions than R. decorum. Photosynthesis and starch and sucrose metabolism shared significant enrichment pathways in R. griersonianum and R. decorum. However, differences in gene-expression patterns related to these pathways existed in response to pH treatments. Furthermore, several unique enriched pathways and expression patterns were identified between both species. Specifically, the genes involved in porphyrin and chlorophyll metabolism, carotenoid biosynthesis, carbon fixation in photosynthetic organisms, and photorespiration were highly expressed at pH 4.5 and 5.5 in R. griersonianum. Meanwhile, genes related to brassinosteroids, galactose metabolism, phenylpropanoids, and flavonoid biosynthesis were identified in R. decorum. This finding implied the different strategies of Rhododendron species during response and adaptation to soil pH conditions. The present study provided new insights to understand the molecular mechanisms of woody plant adaptation to acidic environment.