The 13-lipoxygenase MSD2 and the w-3 fatty acid desaturase MSD3 impact Spodoptera frugiperda resistance in Sorghum

Authors: Block, Anna; Xin, Zhanguo; Christensen, Shawn

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2020
Publication Date: 9/23/2020
Citation: Block, A.K.; Xin, Z; and Christensen, S.A. 2020 The 13-lipoxygenase MSD2 and the w-3 fatty acid desaturase MSD3 impact Spodoptera frugiperda resistance in Sorghum. Planta 252:62 https://doi:10.1007/s00425-020-03475-2
DOI: https://doi.org/10.1007/s00425-020-03475-2

Interpretive Summary: Two important attributes of successful agricultural crops are high yield and pest resistance. A major hurdle to crop improvement is that increasing one of these attributes is often detrimental to the other. USDA Scientists have previously identified two mutants in the important forage crop sorghum, that have increased seed number and thus a higher yield. To check whether this yield increase has a detrimental impact on pest resistance, USDA Scientists now examined how these mutant lines perform when infested with the important insect pest fall armyworm. It was found that both mutant lines had decreased pest resistance but that the impact was much larger on one of the two lines. These results suggest that the mutant which has less impact on pest resistance would be the preferred line to use in sorghum improvement strategies.

Technical Abstract: Jasmonic acid (JA) is a phytohormone that regulates both plant developmental and stress responses. In Sorghum bicolor (sorghum) the '-3 fatty acid desaturase multiseeded3 (msd3) and the 13-lipoxigenase multiseeded2 (msd2) are important for producing JA to regulate panicle development and spikelet fertility. In this study we examined whether these genes are also important for the production of JA in response to herbivory by the insect pest Spodoptera frugiperda. Compared to wild type controls, the msd3 mutant accumulated less JA in leaves of both infested and un-infested plants, revealing that msd3 is involved in both developmental and stress-induced JA production. In contrast, herbivore-induced JA production in the msd2 mutant was indistinguishable from wild type, indicating that it functions primarily in developmental related JA production. An increase of S. frugiperda growth was observed on both the mds3 and mds2 mutants, hinting at roles for both JA and additional oxylipins in sorghum’s defense responses.