Background: Oil flax (linseed, Linum usitatissimum L.) is one of the most important oil crops., However, the increases in drought resulting from climate change have dramatically reduces linseed yield and quality, but very little is known about how linseed coordinates the expression of drought resistance gene in response to different level of drought stress (DS) on the genome-wide level.Results: To explore the linseed transcriptional response of DS and repeated drought (RD) stress, we determined the drought tolerance of different linseed varieties. Then we performed full-length transcriptome sequencing of drought-resistant variety (Z141) and drought-sensitive variety (NY-17) under DS and RD stress at the seedling stage using single-molecule real-time sequencing and RNA-sequencing. Gene Ontology (GO) and reduce and visualize GO (REVIGO) enrichment analysis showed that upregulated genes of Z141 were enriched in more functional pathways related to plant drought tolerance than those of NY-17 were under DS. In addition, 4436 linseed transcription factors were identified, and 1190 were responsive to stress treatments. Moreover, protein-protein interaction (PPI) network analysis showed that the proline biosynthesis pathway interacts with stress response genes through RAD50 (DNA repair protein 50) interacting protein 1 (RIN-1). Finally, proline biosynthesis and DNA repair structural gene expression patterns were verified by RT- PCR.Conclusions: The drought tolerance of Z141 may be related to its upregulation of drought tolerance genes under DS. Proline may play an important role in linseed drought tolerance by maintaining cell osmotic and protecting DNA from ROS damage. In summary, this study provides a new perspective to understand the drought adaptability of linseed.

Background: Oil flax (linseed, Linum usitatissimum L.) is one of the most important oil crops., However, the increases in drought resulting from climate change have dramatically reduces linseed yield and quality, but very little is known about how linseed coordinates the expression of drought resistance gene in response to different level of drought stress (DS) on the genome-wide level.Results: To explore the linseed transcriptional response of DS and repeated drought (RD) stress, we determined the drought tolerance of different linseed varieties. Then we performed full-length transcriptome sequencing of drought-resistant variety (Z141) and drought-sensitive variety (NY-17) under DS and RD stress at the seedling stage using single-molecule real-time sequencing and RNA-sequencing. Gene Ontology (GO) and reduce and visualize GO (REVIGO) enrichment analysis showed that upregulated genes of Z141 were enriched in more functional pathways related to plant drought tolerance than those of NY-17 were under DS. In addition, 4436 linseed transcription factors were identified, and 1190 were responsive to stress treatments. Moreover, protein-protein interaction (PPI) network analysis showed that the proline biosynthesis pathway interacts with stress response genes through RAD50 (DNA repair protein 50) interacting protein 1 (RIN-1). Finally, proline biosynthesis and DNA repair structural gene expression patterns were verified by RT- PCR.Conclusions: The drought tolerance of Z141 may be related to its upregulation of drought tolerance genes under DS. Proline may play an important role in linseed drought tolerance by maintaining cell osmotic and protecting DNA from ROS damage.. In summary, this study provides a new perspective to understand the drought adaptability of linseed.

Background Oil flax (Linum usitatissimum L.) also as known as linseed is one of the most important oil crops in the world. Although linseed was reported to show better tolerance to abiotic stress conditions compared to other oil crops, the molecular mechanisms underlying linseed tolerance to drought stress are largely unknown. Moreover, as a result of climate change, drought dramatically reduces linseed yield and quality, but so far very little is known about how linseed coordinates the drought-resistant genes expression of response to different level of drought stress on the genome-wide level. Results To explore the transcriptional response of linseed to drought stress (DS) and repeated drought stress (RD), we first determined the drought tolerance of different linseed varieties. Then we performed full-length transcriptome sequencing of drought-resistant variety (Z141) and drought-sensitive variety (NY-17) using single-molecule real-time sequencing and RNA-sequencing under drought stress (DS) and repeated drought stress (RD) at the seedling stage. Gene Ontology (GO) enrichment analysis showed that compared with NY-17, the up-regulated genes of Z141 were enriched in more functional pathways related to plant drought tolerance under drought stress. In addition, the number of up-regulated genes in linseed under RD was more 30% than it under DS. In addition, a total of, 4,436 linseed transcription factors were identified, of these, 1,190 genes were responsive to stress treatments. Finally, the expression patterns of proline biosynthesis and DNA repair structural genes were verified by RT- PCR. Conclusions Drought tolerance of Z141 may be related to its specifically up-regulated drought tolerance genes under drought stress. Several variable physiological responses occurred in repeated than in sustained drought treatment. Sum up, this study provides a new perspective to understand the drought adaptability of linseed.