Link Found Between GRF genes in Sorghum and Aphid Resistance
Sorghum, the fifth most important cereal crop, provides food for more than a half billion people. It is also used as livestock feed and as a key component in biofuel. Biotic and abiotic stress resistant, sorghum is an ideal crop to be grown under adverse circumstances like poor soil or water stress conditions. Growth Regulating Factors (GRFs), which encode transcription factors regulating plant growth and development, also respond to changes in the environment. The study identified 8 Sorghum GRF genes containing QLQ (glutamine, leucine, glutamine) and WRC (tryptophan, arginine, cysteine) domains, which evolved in 4 clades. Understanding the role of the GRF gene family in pest resistance could contribute to the development of aphid resistant sorghum, which is of great interest to scientists, growers and breeders alike.
In an effort to better understand this role, Shi et al. from Shanghai Jiao Tong University, Hebei Academy of Agriculture & Forestry Sciences, Hebei Branch of China National Sorghum Improvement Center, Hebei Nijiao Brewing Technology Innovation Center, and Hebei Seed Management Station, identified eight GRF genes in the sorghum genome, evaluating their functional domain architecture and expression patterns under both normal and stressed (heat, salt, drought, aphid) conditions. These SbGRF genes were found to be expressed in most tissues and over half of them (including SbGRF1, 2, 3, 6, 7) expressed at the highest level in inflorescence. The expression level in inflorescence (flower clusters) is indicative of the role of GRFs in growth regulation. The authors hypothesize that flower development may be repressed by down-regulated SbGRFs and ectopic expression of the genes may increase the yield and biomass of sorghum plants.
The researchers performed a transcriptional analysis and discovered that more than half of the SbGRFs responded to abiotic stressors (heat, salinity and drought). This confirms the findings of other studies (Casadevall et al., 2013; Fina et al., 2017, Cao et al., 2020, Kim et al., 2012). However, the effects of biotic stressors, such as insects, on GRF expression has not been the focus of much study. The researchers found that the expression of SbGRF1, 2, 4 and 7 was greatly enhanced when sorghum plants were exposed to aphid stress. This indicates that GRFs help sorghum plants to defend against attacks from pests. The SbGRF response to aphids was validated by qRT-PCR. The results of this study could be used to target certain sorghum GRF genes for selective breeding in an effort to create aphid-resistant cultivars.
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