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

Masson pine (Pinus massonianaLamb.) 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 ofP. massonianaWRKY (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, theP. massonianaWRKY 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 17PmWRKYsin masson pine under different Pi stresses were systematically established using real-time quantitative RT-PCR analysis. Analysis demonstrates that the candidatePmWRKYswere involved in responses to Pi starvation-for example,PmWRKY11,12, and13were upregulated both in P-1(Phosphorus content of 0.01 mM) and P-2(Phosphorus content of 0.06 mM) stresses. The available evidence conclusively sheds light on protein structures, evolutionary relationships, and expression patterns ofWRKYsin 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.