MAPK Gene Family in Lactuca sativa: Genome-Wide Identification, Regulatory Network, and Expression Patterns in Stem Development and Stress Responses

Abstract

Mitogen-activated protein kinases (MAPKs) play essential roles in the process of stress response and plant growth and development. MAPK family genes have been identified in many plant species. In this study, 18 LsMAPK genes were identified in lettuce (Lactuca sativa). The LsMAPK members were divided into Group A, B, C, and D by phylogenetic tree analysis among Arabidopsis, rice, and lettuce. Cis-elements, which relate to abiotic stress, phytohormone response, and transcription factor binding site, were identified to exist in the promoter region of LsMAPK genes. Chromosomal location analysis showed the LsMAPK genes were distributed on eight chromosomes except chromosome 6. Interaction network analysis showed that LsMAPKs could interact with MAPK kinase (MAPKK), protein-tyrosine-phosphatase (PTP), and transcription factors (WRKY, bZIP). Quantitative reverse transcription PCR (qRT-PCR) showed that LsMAPK genes were induced by different abiotic stresses, hormone response, and stem enlargement. The comprehensive identification and characterization of LsMAPK genes in stem lettuce will lay a theoretical foundation for the functional analysis of LsMAPK genes and advance our knowledge of the regulatory mechanism of MAPK genes in plants.