Transcriptome-Wide Identification and Expression Profiles of Masson Pine WRKY Transcription Factors in Response to Low Phosphorus Stress

Abstract

Masson pine (Pinus massoniana Lamb.) is an economically important conifer tree that can be widely used for timber, pulp, and resin production. However, the phosphate (Pi) deficiency in tropical and subtropical forest soils poses severe challenges for the productivity of masson pine. WRKY transcription factors (TFs) have been proven to play important roles in plant responses to biotic and abiotic stresses, including low Pi stress; however, little is known about their roles in masson pine. To understand the roles of P. massoniana WRKY (PmWRKY) in low Pi stress, 25 putative WRKY TFs with complete WRKY domain from transcriptome sequencing data were identified. Based on their conserved domains and zinc-finger motif, the P. massoniana WRKY were divided into three groups. Structural feature analysis shows that PmWRKY proteins contain WRKYGQK/GKK/GRK domains and a C2H2/C2HC-type zinc-finger structure. To putatively identify the function of PmWRKY members involved in low Pi stress, transcriptional profiles of 17 PmWRKYs in masson pine under different Pi stresses were systematically established using real-time quantitative RT-PCR analysis. Analysis demonstrates that the candidate PmWRKYs were involved in responses to Pi starvation—for example, PmWRKY11, 12, and 13 were upregulated both in P1 (Phosphorus content of 0.01 mM) and P2 (Phosphorus content of 0.06 mM) stresses. The available evidence conclusively sheds light on protein structures, evolutionary relationships, and expression patterns of WRKYs in response to low Pi stress of masson pine, which facilitates further functional identification and molecular breeding for the enhancement of low-phosphorous tolerance in this species.