Differential gene expression analysis of the resprouting process in Pinus canariensis provides new insights into a rare trait in conifers

Abstract

Resprouting is crucial in population dynamics in response to wildfires or herbivory. This trait, common in angiosperms, is considered rare in conifers, being Pinus canariensis one of the few species able to resprout. We analyzed gene expression during wound-induced resprouting in 5 years-old Canarian pines. RNA was extracted at three different stages, including control samples from remote branches, representing immediate response to wounding (R0), resprouting initiation (R1), and elongation (R2), and then hybridized to a microarray designed with 15,000 cDNAs from Pinus canariensis transcriptome of meristematic activity. We found 1164 Differentially Expressed Genes (DEGs), of which 903 were significant in R0, 278 in R1, and 261 in R2. Genes related to defense- and stress-response were mainly found to be overexpressed at R0, while DEGs coding for transcription factors such as GROWTH-REGULATING FACTOR (GRF), FLOWERING-PROMOTING FACTOR (FPF), and the HOMEODOMAIN LEUCINE ZIPPER Class IV (HD-ZIP IV), mainly related to outgrowth processes and lateral organogenesis in plants, showed overexpression at R1 and R2, when new shoots were emerging. This data was compared to differential gene expression during apical growth in P. canariensis, suggesting similarities between vegetative apical growth and regulation of lateral shoot development in response to mechanical wounding, but also yielding 32 DEGs exclusively overexpressed at some point during resprouting stages (R1 and/or R2). The implication of such transcription factor families, with important roles in leaf and inflorescence development also in flowering plants, suggests underlying homologies between common lateral organogenesis processes in angiosperms and resprouting in gymnosperms.