Proteomics analysis indicates greater abundance of proteins involved in major metabolic pathways in Lactuca sativa cv. Salinas than Lactuca serriola accession US96UC23

Authors: Adhikari, Neil; Eriksen, Renee; SHI, AINONG - University Of Arkansas; Mou, Beiquan

Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2020
Publication Date: 7/16/2020
Citation: Adhikari, N.D., Eriksen, R.L., Shi, A., Mou, B. 2020. Proteomics analysis indicates greater abundance of proteins involved in major metabolic pathways in Lactuca sativa cv. Salinas than Lactuca serriola accession US96UC23. Proteomics. 20(19-20). Article 1900420. https://doi.org/10.1002/pmic.201900420.
DOI: https://doi.org/10.1002/pmic.201900420

Interpretive Summary: Lettuce (Lactuca sativa L.) is an important commodity and is economically the most important leafy green vegetable in the U.S. Genomes of both cultivated lettuce (cultivar Salinas) and its wild relative L. serriola ( accession US96UC23) have been sequenced. However, we currently lack information about the proteomes of the two species. Our study fills in this gap by using tandem mass tag-based labeling and highly accurate and sensitive mass spectrometry to study the differences in protein levels between the two species under control conditions. Our results suggest significantly lower flux through many essential metabolic pathways in US96UC23 compared to ‘Salinas’. Perturbations in phytochrome signaling may be one possible cause of the shorter stature of L. sativa that needs further study, and higher quantity and/or activity of Fatty Acid Desaturase 2 enzyme, known to contribute to tolerance to many abiotic stresses, may be an important reason behind higher abiotic stress tolerance in US96UC23 and L. serriola in general. This study provides an understanding of the difference in physiology and phenotype of the two species. It also provides the first reference proteome for researchers studying lettuce biology for answering fundamental questions as well as for improving agronomically important traits.

Technical Abstract: Lettuce (Lactuca sativa), cultivated mainly for its edible leaves and stems, is an important vegetable crop worldwide. Genomes of cultivated lettuce (L. sativa cv. Salinas) and its wild relative L. serriola accession US96UC23 have been sequenced, but we don’t have a clear understanding of the genetic basis for divergence in phenotypes of the two species. We used tandem mass tag (TMT) based mass spectrometry to quantitatively compare protein levels between these two species. Four-day old seedlings were transplanted into 500 ml pots filled with soil. Plants were grown for 8 weeks under 250 µmol m-2 sec-1 continuous light, 20°C and relative humidity between 50-70%. Leaf discs (1 cm diam) from three individuals per replicate were analyzed. A total of 3,166 proteins were identified, of which 768 were significantly different between ‘Salinas’ and US96UC23. Pathway analysis indicated a higher flux of carbon in ‘Salinas’ than US96UC23. Many essential metabolic pathways such as tetrapyrrole metabolism and fatty acid biosynthesis were upregulated in ‘Salinas’ compared with US96UC23. This study provides a reference proteome for researchers interested in understanding lettuce biology and improving traits for cultivation.