Expansins: Prospective Determinants of Leaf Angle in Sorghum Bicolor — 68p — Jack R. Erickson, Aeson Akins, Schaler Starks, Ayman Abdulhafiz, Grace Schavee, Martha I. Natukunda

Affiliation: Department of Biology, Augustana University

Leaf angle, the inclination between the leaf blade’s midrib and the plant’s main stem, is an important trait that affects the rate of photosynthesis and yield. The number of cells in collar tissue and the size of these cells determines the leaf angle. The more elongated the cells on the upper surface of the collar tissue are, the more the leaf bends away from the main plant stem and the larger the leaf angle. Researchers have proposed an ideal canopy for cereals such as sorghum, the fifth most important cereal crop in the world and the third most important in the United States. In this proposed canopy (“smart canopy”), the angles of leaves are larger near the plant’s base, and they get progressively smaller up the plant. Unfortunately, sorghum displays the inverse of the smart canopy model, suggesting that improving the leaf arrangement could increase photosynthetic efficiency and yield. We aim to study expansins, genes whose proteins are involved in cell elongation. Based on previous RNA-seq datasets, we identified five candidate expansins whose expression was higher in the middle sorghum canopy compared to the lower layer. We hypothesized that the higher gene expression could contribute to more elongated cells and larger leaf angles. We utilized polymerase chain reaction (RT- and RT-qPCR) to compare the expression of the candidates between the middle and lower canopy layers of sorghum to validate the previous results. Our preliminary results show that three of the genes have higher expression (P<0.05) in the middle canopy compared to the lower canopy, while the other two exhibit no differences. More experiments will be conducted to confirm the observed results. Long-term, genetic knockout studies will be conducted to determine the exact role of expansins in leaf angle determination.

Augustana University
Dr. Ibore-Natakunda