Identification and Characterization of Wall-Associated Kinase (WAK) and WAK-like (WAKL) Gene Family in Juglans regia and Its Wild Related Species Juglans mandshurica

Abstract

Wall-associated kinase (WAK) and WAK-like kinase (WAKL) are receptor-like kinases (RLKs), which play important roles in signal transduction between the cell wall and the cytoplasm in plants. WAK/WAKLs have been studied in many plants, but were rarely studied in the important economic walnut tree. In this study, 27 and 14 WAK/WAKL genes were identified in Juglans regia and its wild related species Juglans mandshurica, respectively. We found tandem duplication might play a critical role in the expansion of WAK/WAKL gene family in J. regia, and most of the WAK/WAKL homologous pairs underwent purified selection during evolution. All WAK/WAKL proteins have the extracellular WAK domain and the cytoplasmic protein kinase domain, and the latter was more conserved than the former. Cis-acting elements analysis showed that WAK/WAKL might be involved in plant growth and development, plant response to abiotic stress and hormones. Gene expression pattern analysis further indicated that most WAK/WAKL genes in J. regia might play a role in the development of leaves and be involved in plant response to biotic stress. Our study provides a new perspective for the evolutionary analysis of gene families in tree species and also provides potential candidate genes for studying WAK/WAKL gene function in walnuts.

Genome-Wide Identification and Expression Analysis of Wall-Associated Kinase (WAK) Gene Family in Cannabis sativa L.

“…The homolog of CsWAKL1 and CsWAKL7, Juglans regia WAK2 and WAKL13, respectively, are mainly expressed in female flowers. JrWAK9, the homolog of CsWAK1, is involved in pathogen response [ 12 ]. AtWAKL22 gene, the homolog of CsWAK 7, is responsible for dominant resistance against several Fusarium races [ 30 ].…”

“…Recently, a genome-wide analysis of wall-associated kinase gene families in several species was published. The number of WAK/WAKLs identified in Oryza sativa was 125 [ 6 ], 115 in Brachypodium [ 7 ], 39 in Solanum lycopersicum [ 8 ], 58 in Gossypium arboreum, 66 in G. raimondii, 99 in G. hirsutum [ 9 ], (Zhang et al 2021), 68 in Rosa chinensis [ 10 ], 91 in Hordeum vulgare [ 11 ], 22 in Juglans regia [ 12 ], 175 in Populus trichocarpa [ 13 ], and more than 100 in Zea mays [ 14 ]. The number of WAK genes in monocot crops seems to be quite large compared with Arabidopsis as a dicot, implying possible gene duplication during domestication [ 15 ].…”

Characterization of the WAK Gene Family Reveals Genes for FHB Resistance in Bread Wheat (Triticum aestivum L.)

“…Moreover, WAK gene duplication events have been reported in other plant species such as cotton, rice, J. regia, and J. mandshurica. Thus, whole-genome and segmental duplications are among the common causes of WAK gene family expansion in different species [26,27,29]. The syntenic relationship revealed the presence of 101 and 34 orthologous gene pairs between wheat and H. vulgare and O. sativa, respectively, and only one orthologous gene pair between wheat and G. max.…”

“…Characterizing the WAK gene family will help identify many new candidate genes that may contribute to disease resistance. Presently, WAK gene families have been identified and characterized in diverse plant species, including 26 members in Arabidopsis [3], 125 in rice [27], 91 in barley [28], 27 in walnuts [29], 29 in tomato [25], 29 in potato [36], and 29 in cotton [26]. Although several wheat WAKs have been reported, their genome-wide characterization in the complicated wheat hexaploid genome is lacking.…”

“…Genome sequences can provide valuable information for genome-based investigations. To date, the WAK gene family has been comprehensively identified in various plant species such as Arabidopsis [3], tomato [25], cotton [26], rice [27], barley [28], and walnuts [29]. However, systematic investigations of WAKs are yet to be performed in the wheat genome.…”