Transcriptome of weeping pinyon pine, Pinus pinceana, shows differences across heterogeneous habitats

Abstract

We reconstructed the needle tissue Transcriptome of P. pinceana for individuals from distinct biogeographic regions across a temperature and precipitation gradient that represents its natural distribution. Gene expression analysis via RNA-Seq identified differential response to biotic stress. Phenotypic plasticity includes physiological traits affected by subtle changes in mRNA expression levels, causing different molecular phenotypes. We assessed the differential response to climate heterogeneity across the geographic range of Pinus pinceana G. Gordon & Glendinning. This pinyon pine shows a fragmented geographic distribution suggesting adaptation to the arid and extreme conditions of the eastern mountain slopes of the Chihuahuan desert. The geographic distribution of P. pinceana spans regions with significant variation in annual temperature and precipitation. We tested whether phenotypic divergence is supported by differences in expression profiles in P. pinceana mature trees along its natural distribution and corresponds to the changes in drought and other environmental stress. The reconstructed Transcriptome included 45,431 high-quality annotations derived from the needles of seven individuals across contrasting biogeographic and climatic localities. Trees from the driest regions shared active responses related to abiotic factors. The differential expression analysis identified intermediates and regulators of abiotic stress response for 26 genes, highlighting families involved in the environmental response to abiotic stress, and proteins linked to up-regulated responses, such as LRR receptor-like serine/threonine-protein kinase and L-type lectin receptor kinases (LecRK), directly related to pathogens. When Chihuahuan desert samples were compared with arboretum samples, we found differential expression of a regulator of root morphogenesis, cysteine-rich receptor-like protein kinase (CRK28), which could relate to differential absorption in drought conditions.