Comparative transcriptome analysis of genes involved in response to thermal stress and leaf colour change of Acer palmatum

Exterior leaf colour is an important trait for ornamental foliage plants. Accumulating evidence indicates that thermal stress (TS) has a significant effect on the colour of plant leaves, but the molecular mechanism underlying TS-induced change in leaf colour between red and green of Acer palmatum is poorly understood. In this study, a comparative transcriptome analysis was performed using RNA-seq, in which A. palmatum was exposed to 23 degrees C for 4 d (A1_23) and 8 d (A2_23) and 28 degrees C for 4 d (A1_28) and 8 d (A2_28). There were 20,146 (12,304 up and 7842 down) and 9570 (3700 up and 5870 down) differentially expressed genes (DEGs) in the A1_28 and A2_28 samples compared to the A1_23 and A2_23 samples, respectively. Three hundred forty-six DEGs were co-upregulated, and 640 DEGs were co-downregulated in A1_28 and A2_28. Bioinformatics analyses revealed that A. palmatum cell resistance to TS occurs through upregulated interacting Hsp90-Hsp83-Hsp20 and GST-GSH-HSPs or through small Hsps genes and sterol biosynthesis genes that regulate membrane fluidity. In addition, our results demonstrated that A. palmation leaves reduce the expression of the negative regulator PP2C and interleukin receptor kinase to activate PP2C substrates, such as MAPK, to regulate TS signalling pathways. Moreover, our results showed that the anthocyanin and carotenoids biosynthetic related genes significantly upregulated, and the chlorophyll biosynthetic and chloroplast constitutive related genes significantly downregulated, which were the direct molecular mechanisms of TS changing leaf colour from red return to green in A. pairriatum. Our findings provide key genetic resources for further investigation of the molecular mechanisms of TS changing leaf colour in A. palmatum and other related species.