Abstract
BackgroundTransgenic poplar (Populus × euramericana 'Guariento') plants harboring five exogenous, stress-related genes exhibit increased tolerance to multiple stresses including drought, salt, waterlogging, and insect feeding, but the complex mechanisms underlying stress tolerance in these plants have not been elucidated. Here, we analyzed the differences in the transcriptomes of the transgenic poplar line D5-20 and the non-transgenic line D5-0 using high-throughput transcriptome sequencing techniques and elucidated the functions of the differentially expressed genes using various functional annotation methods.ResultsWe generated 11.80 Gb of sequencing data containing 63, 430, 901 sequences, with an average length of 200 bp. The processed sequences were mapped to reference genome sequences of Populus trichocarpa. An average of 62.30% and 61.48% sequences could be aligned with the reference genomes for D5-20 and D5-0, respectively. We detected 11,352 (D5-20) and 11,372 expressed genes (D5-0), 7,624 (56.61%; D5-20) and 7,453 (65.54%; D5-0) of which could be functionally annotated. A total of 782 differentially expressed genes in D5-20 were identified compared with D5-0, including 628 up-regulated and 154 down-regulated genes. In addition, 196 genes with putative functions related to stress responses were also annotated. Gene Ontology (GO) analysis revealed that 346 differentially expressed genes are mainly involved in 67 biological functions, such as DNA binding and nucleus. KEGG annotation revealed that 36 genes (21 up-regulated and 15 down-regulated) were enriched in 51 biological pathways, 9 of which are linked to glucose metabolism. KOG functional classification revealed that 475 genes were enriched in 23 types of KOG functions.ConclusionThese results suggest that the transferred exogenous genes altered the expression of stress (biotic and abiotic) response genes, which were distributed in different metabolic pathways and were linked to some extent. Our results provide a theoretic basis for investigating the functional mechanisms of exogenous genes in transgenic plants.
Highlights
Transgenic poplar (Populus × euramericana ‘Guariento’) plants harboring five exogenous, stress-related genes exhibit increased tolerance to multiple stresses including drought, salt, waterlogging, and insect feeding, but the complex mechanisms underlying stress tolerance in these plants have not been elucidated
Genes of interest that can be used in the genetic engineering of abiotic stress-resistant plants can be divided into two categories: 1) genes that directly respond to stress, which mainly include genes encoding functional proteins that protect the cell against stress damage, such as enzymes for the synthesis of osmolytes, and enzymes for the removal of active oxygen; 2) genes that regulate genetic expression and signal transduction under stress, which mainly include genes encoding transcription factors, protein kinases, and others
We found that 34 genes encoding serine/threonine protein kinases were up-regulated in the transgenic clones (D5-20), including 17 receptor-like kinases with leucinerich replicated region, two mitogen-activated protein kinase (MAPK), and two lectin-like kinase; five other serine/threonine protein kinases in D5-20 were down-regulated
Summary
Transgenic poplar (Populus × euramericana ‘Guariento’) plants harboring five exogenous, stress-related genes exhibit increased tolerance to multiple stresses including drought, salt, waterlogging, and insect feeding, but the complex mechanisms underlying stress tolerance in these plants have not been elucidated. Some genes are involved in the expression of osmolytes, such as proline, glycine, betaine, sucrose, fructan, and so on, and they help plants accumulate osmolytes to maintain the osmotic balance and body moisture levels, which improves the drought tolerance of plants under drought and salt stress [2]. Transporter genes can help alter the ionic and osmotic balance in plants by up-regulating the expression levels of proteins to control ion transport under abiotic stress [8]; for example, HAL1 expression improves the salt tolerance of transgenic tomatoes [9]. VHb gene expression can facilitate the growth of transgenic Nicotiana tabacum [11,12], Datura innoxia [13], and Petunia hybrida Vilm [14]
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