Characterization of LiMAPK gene in response to salinity stress in Tiger lily (Lilium lancifolium Thunb.)

Abstract

In this study, we measured the physiological response such as relative growth rate (RGR), relative water content (RWC), chlorophyll index, net photosynthetic rate and relative electrical conductivity of Tiger lily leaves periodically, under different concentrations of salt. We isolated LiMAPK mRNA (including the 5′ UTR and 3′ UTR) (GenBank accession number JQ437268) under treatment at salt threshold concentrations by rapid amplification of cDNA ends polymerase chain reaction (RACE–PCR). The relative expression levels of LiMAPK under salt stress were analyzed by real-time fluorescence quantitative PCR. The results showed that the salt threshold concentration of Tiger Lily was 1.09 mg/mL, and the LiMAPK gene covered 1291 bp, coded 306 amino acids and the conservative domain was 627 bp long. There was a highly conserved domain (TRWYRAPE) present in the amino acid sequence of MAPK. Comparative analysis using NCBI BLASTp showed that this conservative domain was a catalytic domain in the MAPK super family. The LiMAPK expression levels in the leaves were significantly increased within 2 h after initiation of stress treatment with salt threshold concentrations and continued to rise in the next 2 h, reaching a maximum at 4 h and decreasing in the next 4 h. After 12 and 24 h of salt stress, the LiMAPK expression levels were basically stable, but still twice as high as those in the control. The results indicated that the LiMAPK gene was up-regulated by salt stress, which might be closely related to the salt-tolerance mechanism in Tiger lily.