A Comprehensive Identification and Expression Analysis of the WUSCHEL Homeobox-Containing Protein Family Reveals Their Special Role in Development and Abiotic Stress Response in Zea mays L.

Abstract

Maize is an important food and cash crop worldwide. The WUSCHEL (WUS)-related homeobox (WOX) transcription factor (TF) family plays a significant role in the development process and the response to abiotic stress of plants. However, few studies have been reported on the function of WOX genes in maize. This work, utilizing the latest maize B73 reference genome, results in the identification of 22 putative ZmWOX gene family members. Except for chromosome 5, the 22 ZmWOX genes were homogeneously distributed on the other nine chromosomes and showed three tandem duplication and 10 segmental duplication events. Based on phylogenetic characteristics, ZmWOXs are divided into three clades (e.g., WUS, intermediate, and ancient groups), and the majority of ZmWOXs in same group display similar gene and protein structures. Cross-species collinearity results indicated that some WOX genes might be evolutionarily conservative. The promoter region of ZmWOX family members is enriched in light, plant growth/hormone, and abiotic stress-responsive elements. Tissue-specific expression evaluation showed that ZmWOX genes might play a significant role in the occurrence of maize reproductive organs. Transcriptome data and RT-qPCR analysis further showed that six ZmWOX genes (e.g., ZmWOX1, 4, 6, 13, 16, and 18) were positively or negatively modulated by temperature, salt, and waterlogging stresses. Moreover, two ZmWOXs, ZmWOX1 and ZmWOX18, both were upregulated by abiotic stress. ZmWOX18 was localized in the nucleus and had transactivation activities, while ZmWOX1 was localized in both the cytoplasm and nucleus, without transactivation activity. Overall, this work offers new perspectives on the evolutionary relationships of ZmWOX genes and might provide a resource for further detecting the biological functions of ZmWOXs.