RNA extraction and gene clone
The roots and nodes of S. alterniflora (0.2 g fresh weight) were ground into powder in liquid nitrogen. The total RNA was extracted by using an RNA purification reagent kits and reverse transcribed into cDNA by using M-MLV reverse transcriptase (TaKaRa, Dalian, China). The homologous genes of different plant species obtained from NCBI database were aligned and used to design the degenerate primers (Supplementary Table S2). The amplified products were sequencing and the sequences were search in NCBI database (Supplementary Table S3). After that, the identified sequences were used to design the gene-specific primers for quantitative real-time PCR (qRT-PCR) (Supplementary Table S4).