Seed oil storage in three contrasted legume species: implications for oil improvement

Cellular comparisons on three legume species indicate oil body size is factor in mediating oil content. Key transcription factors and oleosins determining seed oil content were identified in somatic embryos of Medicago. Legume seeds provide a significant oil alternative to meat fat needs. Increasing demand for oil nutrition in the context of sustainable crop production has stimulated the exploration of legume seed oil storage regulation. This study investigated the cellular characteristics of seed oil storage using three legume species i.e. Medicago truncatula, Glycine max and Pongamia pinnata representing different oil/protein ratios, and then examined in vitro approaches for assessing strategies in enhancing seed oil storage. A greater range of oil body sizes was in higher oil/protein content species, with highest species having the largest oil bodies; and the smallest oil body size being relatively similar across species, suggesting that the arrangement of oil body size may be factor in mediating oil content. The expression of four key transcription factors i.e. LEC1, L1L, FUS3 and ABI3, and four oleosin genes in determining seed oil content was compared in vivo and in vitro using somatic embryos in Medicago, along with cellular evidence of oil bodies in somatic embryos, indicating that somatic embryos may be suitable models for rapid assessment of seed oil enhancement. This study revealed the cellular characteristics for legume seed oil storage with different nutritional compositions, and identified the associated molecular basis for boosting seed oil storage via regulating oil body size. In addition, somatic embryogenesis may be an effective system for examining oil production by modifying the expression of candidate genes prior to in vivo testing.