Genome-Wide Characterization of the Mitogen-Activated Protein Kinase Gene Family and Their Expression Patterns in Response to Drought and Colletotrichum Gloeosporioides in Walnut (Juglans regia)

Abstract

Mitogen-activated protein kinases (MAPKs) are a family of Ser/Thr (serine/threonine) protein kinases that play very important roles in plant responses to biotic and abiotic stressors. However, the MAPK gene family in the important crop walnut (Juglans regia L.) has been less well studied compared with other species. We discovered 25 JrMAPK members in the Juglans genome in this study. The JrMAPK gene family was separated into four subfamilies based on phylogenetic analysis, and members of the same subgroup had similar motifs and exons/introns. A variety of cis-acting elements, mainly related to the light response, growth and development, stress response, and hormone responses, were detected in the JrMAPK gene promoters. Collinearity analysis showed that purification selection was the main driving force in JrMAPK gene evolution, and segmental and tandem duplications played key roles in the expansion of the JrMAPK gene family. The RNA-Seq (RNA Sequencing) results indicated that many of the JrMAPK genes were expressed in response to different levels of Colletotrichum gloeosporioides infection. JrMAPK1, JrMAPK3, JrMAPK4, JrMAPK5, JrMAPK6, JrMAPK7, JrMAPK9, JrMAPK11, JrMAPK12, JrMAPK13, JrMAPK17, JrMAPK19, JrMAPK20, and JrMAPK21 were upregulated at the transcriptional level in response to the drought stress treatment. The results of this study will help in further investigations of the evolutionary history and biological functions of the MAPK gene family in walnut.

JrPHL8-JrWRKY4-JrSTH2L module regulates resistance to Colletotrichum gloeosporioides in walnut

“…Many chorismate and phenylalanine pathways-related genes PBS3 , S5H , C4H , and COMT were identified through transcriptome analyses during C. gloeosporioides infected walnut fruits [ 43 ]. JrMAPK genes were also found to be up up-regulated expression in response to different levels of C. gloeosporioides infection [ 44 ]. WRKY TFs as an important component of plant immunity have also been identified in the walnut– C. gloeosporioides interaction.…”

A dual RNA-seq analyses revealed dynamic arms race during the invasion of walnut by Colletotrichum gloeosporioides

“…Walnut ( Juglans regia L.) is an important woody oil tree species, which kernels are rich in nutritional value and are beneficial to human health [ 16 , 17 ]. But due to the lack of disease resistant varieties, walnut anthracnose caused by C. gloeosporioides has become a catastrophic disease in walnut production, which can lead to 30–50% yield loss [ 18 , 19 ]. Previous studies have shown that the lifestyle transitions of C. gloeosporioides in infected walnut fruits is initial infection at 24 hpi, biotrophy at 48 hpi, and necrotrophy at 72 hpi [ 20 ].…”