A comparison of the transcriptomes between diploid and autotetraploid Paulownia fortunei under salt stress

Authors: WANG, ZHE - Henan Agricultural University; ZHAO, ZHENLI - Henan Agricultural University; FAN, GUOQIANG - Henan Agricultural University; DONG, YANPENG - Henan Agricultural University; DENG, MINJIE - Henan Agricultural University; XU, ENKAI - Henan Agricultural University; ZHAI, XIAOQIAO - Henan Agricultural University; Cao, Heping

Submitted to: Physiology and Molecular Biology of Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2018
Publication Date: 1/31/2019
Citation: Wang, Z., Zhao, Z., Fan, G., Dong, Y., Deng, M., Xu, E., Zhai, X., Cao, H. 2019. A comparison of the transcriptomes between diploid and autotetraploid Paulownia fortunei under salt stress. Physiology and Molecular Biology of Plants. 25(1):1-11. https://doi.org/10.1007/s12298-018-0578-4.
DOI: https://doi.org/10.1007/s12298-018-0578-4

Interpretive Summary: Paulownia is a genus of fast-growing deciduous trees native to China, where it has been used for afforestation and improvement of the ecological environment. Paulownia species have been introduced in many countries for their important ecological, economic, and social significance. Paulownia has excellent tolerance to extreme soils. Polypidy is found in some organisms, especially common in plants. Many studies have shown that the polyploid plants have larger organs and more biomass than the diploids, and plants with higher ploidy levels seem to be more adaptable to stressful conditions than their diploid relatives. Soil salinization is an increasingly severe agricultural problem that can cause a combination of dehydration and osmotic-related stress effects. Primary sources of salinity include natural processes such as mineral weathering or fluctuations in sea-water levels, along with anthropogenic activities such as irrigation. Of the approximately 230 million hectares of land that can be irrigated worldwide, 45 million hectares were reported to be under salt stress. Various strategies have been proposed regarding the use of the salt-affected lands, including the reclamation of salt-affected soils, halophyte cultivation, and breeding salt-tolerant crops. The mechanisms of salinity tolerance are highly complex processes in which many genes and pathways are involved. In this study, we sequenced the transcriptomes of normal and salt-treated tetraploid and diploid P. fortunei for better understanding the mechanisms of salinity tolerance. We identified two dozens of important differentially expressed unigenes related to photosynthesis, plant growth and development and osmolytes. These DEUs were upregulated in tetraploid compared to diploid and upregulated under salt stress. Our results provided insights into the molecular aspects why tetraploid is stronger and more energetic than diploid under saline environment.

Technical Abstract: Paulownia is a tree species which is grown in many countries. Our previous study reveals that tetraploid Paulownia fortunei is more tolerant to salt stress than its corresponding diploid tree. To investigate the molecular mechanisms of salt stress tolerance in P. fortunei, the transcriptomes of normal and salt-stressed diploid and tetraploid were investigated. After assembling the clean reads, we obtained 130,842 unigenes. The unigenes were then aligned against six public databases (Nr, Nt, Swiss-Prot, COG, KEGG, GO) to find homologs and assign functional annotations. 7,983 and 15,503 differentially expressed unigenes (DEUs) between the normal and the salt-stressed diploid and tetraploid P. fortunei were retrieved, respectively. Quantitative real-time polymerase chain reaction was used to verify the expression patterns of 15 unigenes. We identified two dozens of important differentially expressed unigenes (DEUs) including 3 related to photosynthesis, 10 related to plant growth and development and 11 related to osmolytes. These DEUs were upregulated in tetraploid compared to diploid and upregulated under salt stress. Our results provided insights into the molecular aspects why tetraploid is stronger and more energetic than diploid under saline environment. This study provides useful information for further studies on the molecular mechanisms of salt tolerance in other tree plants.