**Gang Wang, Tao Wang, Zhan-Hui Jia, Ji-Ping Xuan, De-Lin Pan, Zhong-Ren Guo and Ji-Yu Zhang \* ID**

Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China; wg20092011@163.com (G.W.); immmorer@163.com (T.W.); 13915954315@163.com (Z.-H.J.); xuanjiping@cnbg.net (J.-P.X.); PPxsperfect@163.com (D.-L.P.); zhongrenguo@cnbg.net (Z.-R.G.)

**\*** Correspondence: maxzhangjy@163.com; Tel.: +86-025-8434-7033

Received: 16 July 2018; Accepted: 20 August 2018; Published: 24 August 2018

**Abstract:** Mitogen activated protein kinase (MAPK) cascades are universal signal transduction modules that play crucial roles in various biotic and abiotic stresses, hormones, cell division, and developmental processes in plants. Mitogen activated protein kinase (MAPK/MPK), being a part of this cascade, performs an important function for further appropriate cellular responses. Although MAPKs have been investigated in several model plants, no systematic analysis has been conducted in kiwifruit (*Actinidia chinensis*). In the present study, we identified 18 putative MAPKs in the kiwifruit genome. This gene family was analyzed bioinformatically in terms of their chromosome locations, sequence alignment, gene structures, and phylogenetic and conserved motifs. All members possess fully canonical motif structures of MAPK. Phylogenetic analysis indicated that *AcMAPK*s could be classified into five subfamilies, and these gene motifs in the same group showed high similarity. Gene structure analysis demonstrated that the number of exons in *AcMAPK* genes ranged from 2 to 29, suggesting large variation among kiwifruit *MAPK* genes. The expression profiles of these *AcMAPK* genes were further investigated using quantitative real-time polymerase chain reaction (qRT-PCR), which demonstrated that *AcMAPKs* were induced or repressed by various biotic and abiotic stresses and hormone treatments, suggesting their potential roles in the biotic and abiotic stress response and various hormone signal transduction pathways in kiwifruit. The results of this study provide valuable insight into the putative physiological and biochemical functions of *MAPK* genes in kiwifruit.

**Keywords:** mitogen-activated protein kinase (MAPK); kiwifruit; phylogenetic relationships; gene expression; biotic and abiotic stresses
