Dataset Information

Transcriptome analysis of Para rubber tree (H. brasiliensis) seedlings under ethylene stimulation.

ABSTRACT:

Background

Natural rubber (cis-1,4-polyioprene, NR) is an indispensable industrial raw material obtained from the Pará rubber tree (H. brasiliensis). Natural rubber cannot be replaced by synthetic rubber compounds because of the superior resilience, elasticity, abrasion resistance, efficient heat dispersion, and impact resistance of NR. In NR production, latex is harvested by periodical tapping of the trunk bark. Ethylene enhances and prolongs latex flow and latex regeneration. Ethephon, which is an ethylene-releasing compound, applied to the trunk before tapping usually results in a 1.5- to 2-fold increase in latex yield. However, intense mechanical damage to bark tissues by excessive tapping and/or over-stimulation with ethephon induces severe oxidative stress in laticifer cells, which often causes tapping panel dryness (TPD) syndrome. To enhance NR production without causing TPD, an improved understanding of the molecular mechanism of the ethylene response in the Pará rubber tree is required. Therefore, we investigated gene expression in response to ethephon treatment using Pará rubber tree seedlings as a model system.

Results

After ethephon treatment, 3270 genes showed significant differences in expression compared with the mock treatment. Genes associated with carotenoids, flavonoids, and abscisic acid biosynthesis were significantly upregulated by ethephon treatment, which might contribute to an increase in latex flow. Genes associated with secondary cell wall formation were downregulated, which might be because of the reduced sugar supply. Given that sucrose is an important molecule for NR production, a trade-off may arise between NR production and cell wall formation for plant growth and for wound healing at the tapping panel.

Conclusions

Dynamic changes in gene expression occur specifically in response to ethephon treatment. Certain genes identified may potentially contribute to latex production or TPD suppression. These data provide valuable information to understand the mechanism of ethylene stimulation, and will contribute to improved management practices and/or molecular breeding to attain higher yields of latex from Pará rubber trees.

SUBMITTER: Nakano Y

PROVIDER: S-EPMC8436496 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose: de novo sequencing and comparative analysis of the bark transciptomes of Hevea brasiliensis induced without ethephon (C), with ethephon for 8 hours (E8) and 24 hours (E24) to identify the genes and pathways related to the stimulation of rubber production by ethylene. The goals of this study are to reveal the molecular mechanism behind the stimulation of rubber production by ethylene. Methods: Bark RNA was extracted using the TRIzol® Reagent (Invitrogen) and two cDNA libraries, H (healthy rubber trees) and T (TPD-affected trees), were prepared using the mRNA-Seq 8 sample prep Kit (Illumina). The libraries were deep sequenced using Illumina HiSeqTM 2000 (Illumina Inc., San Diego, CA, USA). Raw reads produced from sequencing machines were resorted to de novo assembly and gene annotation. Results: De novo sequencing and assembly of the bark transciptomes of Hevea brasiliensis induced with ethephon for 8 hours (E8) and 24 hours (E24) were performed. 51,965,770, 52,303,714 and 53,177,976 high-quality clean reads from E8, E24 and C (control) samples were assembled into 81,335, 80,048 and 80,800 unigenes respectively, with a total of 84,425 unigenes and an average length of 1,101 bp generated. 10,216 and 9,374 differentially expressed genes (DEGs) in E8 and E24 compared with C were respectively detected. The expression of several enzymes in crucial points of regulation in glycolysis were up-regulated and DEGs were not significantly enriched in isopentenyl diphosphate (IPP) biosynthesis pathway. In addition, up-regulated genes of great regulatory importance in carbon fixation (Calvin cycle) were identified. Conclusions: The rapid acceleration of glycolytic pathway supplying precursors for the biosynthesis of IPP and natural rubber, instead of rubber biosynthesis per se, may be responsible for ethylene stimulation of latex yield in rubber tree. The elevated rate of flux throughout the Calvin cycle may account for some durability of ethylene-induced stimulation. Our finding lays the foundations for molecular diagnostic and genetic engineering for high-yielding improvement of rubber tree.

Project description:Purpose: de novo sequencing and comparative analysis of the bark transciptomes of Hevea brasiliensis induced without ethephon (C), with ethephon for 8 hours (E8) and 24 hours (E24) to identify the genes and pathways related to the stimulation of rubber production by ethylene. The goals of this study are to reveal the molecular mechanism behind the stimulation of rubber production by ethylene. Methods: Bark RNA was extracted using the TRIzolÂ® Reagent (Invitrogen) and two cDNA libraries, H (healthy rubber trees) and T (TPD-affected trees), were prepared using the mRNA-Seq 8 sample prep Kit (Illumina). The libraries were deep sequenced using Illumina HiSeqTM 2000 (Illumina Inc., San Diego, CA, USA). Raw reads produced from sequencing machines were resorted to de novo assembly and gene annotation. Results: De novo sequencing and assembly of the bark transciptomes of Hevea brasiliensis induced with ethephon for 8 hours (E8) and 24 hours (E24) were performed. 51,965,770, 52,303,714 and 53,177,976 high-quality clean reads from E8, E24 and C (control) samples were assembled into 81,335, 80,048 and 80,800 unigenes respectively, with a total of 84,425 unigenes and an average length of 1,101 bp generated. 10,216 and 9,374 differentially expressed genes (DEGs) in E8 and E24 compared with C were respectively detected. The expression of several enzymes in crucial points of regulation in glycolysis were up-regulated and DEGs were not significantly enriched in isopentenyl diphosphate (IPP) biosynthesis pathway. In addition, up-regulated genes of great regulatory importance in carbon fixation (Calvin cycle) were identified. Conclusions: The rapid acceleration of glycolytic pathway supplying precursors for the biosynthesis of IPP and natural rubber, instead of rubber biosynthesis per se, may be responsible for ethylene stimulation of latex yield in rubber tree. The elevated rate of flux throughout the Calvin cycle may account for some durability of ethylene-induced stimulation. Our finding lays the foundations for molecular diagnostic and genetic engineering for high-yielding improvement of rubber tree. De novo sequencing of the transcriptomes of C (bark without ethephon application), E8 (bark with 1.5%-ethephon treatment for 8 hours) and E24 (bark with 1.5%-ethephon treatment for 24 hours) rubber trees was conducted using Illumina HiSeq 2000.