Spatiotemporal Expression and Bioinformatic Analyses of the HD-Zip Transcription Factor Family in Larix olgensis

Abstract

Larix olgensis is one of the main coniferous tree species in northeastern China and has excellent timber properties and strong tolerance to stress. Thirteen HD-Zip family genes with a complete CDS region were identified on the basis of cambium transcriptome data from Larix olgensis. All 13 genes were analyzed via bioinformatics by their conserved domain protein sequence and amino acid composition, including their physicochemical properties and protein structure. The spatiotemporal expression and abiotic stress responses of these genes were analyzed by real-time quantitative PCR. The results showed that the 13 HD-Zip genes of Larix olgensis were expressed in the roots, stems, and leaves at different stages. The expression of three of these genes (LoHDZ2, LoHDZ11, LoHDZ13) was highest in nonlignified roots, indicating that they might be related to the secondary growth of Larix olgensis; in addition, three genes (LoHDZ5, LoHDZ9, LoHDZ10) were highly expressed in partially and completely lignified stems and leaves. These 13 genes were expressed specifically under drought stress. The expression of two of them (LoHDZ1, LoHDZ5) was obviously upregulated, and the expression of 6 genes (LoHDZ2, LoHDZ3, LoHDZ4, LoHDZ8, LoHDZ10, LoHDZ13) was significantly downregulated. The expression trends indicate that these genes could be involved in drought stress. The expression of all 13 genes was downregulated when the plants were treated with 0.2 M NaCl for 96 h, indicating that these genes are inhibited by salt stress. Overall, the results have significant implications for the study of the gene function of members of the LoHD-Zip transcription factor family.