Authors: Raymond N. Mutava¹, Naeem H. Syed², Silvas J. Prince¹, Henry T. Nguyen¹

¹Molecular Genetics and Soybean Genomics Laboratory, University of Missouri, Columbia, MO 65211, USA

²School of Human and Life Sciences, Canterbury Christ Church University, Canterbury, CT1 1QU, United Kingdom

Abstract

Drought stress causes significant yield losses in crops like soybean (Glycine max). Sources of drought and flooding tolerance have been found in soybean and have been used to improve soybean yields under drought and flooding conditions. The underlying molecular and physiological mechanisms for drought and flooding tolerance are poorly understood. To evaluate soybean response to drought and flooding stress at the physiological, cellular and molecular level, four contrasting lines: PI 567690 - drought tolerant (DT), Pana - drought susceptible (DS), PI 408105A - flooding tolerant (FT), S99-2281 - flooding susceptible (FS) were grown under greenhouse conditions and subjected to drought (21 days) and flooding (15 days) stress starting from V5 stage. Leaf tissue was used for anatomical, biochemical and whole genome transcriptome analysis. We found significant variation in plastoglobules size and numbers as well as starch granule accumulation under drought and flooding suggesting a possible role of plastoglobules and some Fibrillin proteins in soybean response to drought and flooding stress. Drought transcriptome between PI 597387 (DS) and PI 567690 (DT) lines detected an up-regulation of genes associated with UDP glucoronosyl transferase activity. We also found conserved SNP variation in some key aquaporin genes which could potentially be used as functional markers for selecting canopy wilting/drought tolerant trait in soybean. Many clock and SUB1 genes were differential expressed under flooding and drought conditions and we found variation in the amplitude and phase shifts in PRR7 and TOC1 genes under drought and flooding conditions, respectively. This suggests the potential for using clock genes with variation in phase and period to screen exotic germplasm for tolerance to drought and flooding as well as the prospects of fine tuning multiple circadian clock to develop more resilient soybean varieties in the face of climate change.