Effects of Glucosinolates on Plant Physiology during Sulfur Deprivation
Glucosinolates (GSLs) are sulfur-rich, specialized plant metabolites that underlie the chemical diversity and biotic stress responses found in the order Brassicales. Sulfur, an essential but limited plant nutrient, is a critical component in amino acids (cysteine; methionine) and stress related, specialized metabolites (glutathione; GSLs). Variation in sulfur availability (sulfur pools) for primary and specialized metabolism has pronounced effects on plant health and physiology. Crops in the genus Brassica (oilseed varieties; cruciferous vegetables), which are sister to the model plant Arabidopsis, are chemically diverse and have varying sulfur requirements. Understanding the tradeoffs associated with sulfur intensive metabolites (GSLs) and plant growth is integral in our ability to maintain healthy and productive crops. To explore these tradeoffs, I designed a series of vertical growth (root length) assays using Arabidopsis thaliana lines that either have a key GSL biosynthetic gene knocked out (myb28, myb29), overexpressed (myb29OE), or at wild-type levels (Col-0). Plants were grown on sulfur depleted media and transferred to sulfur sufficient media (½ strength) at varying times of day (morning; evening) to explore when sulfur additions are more beneficial to growth. In a previous pilot study, I observed that accumulation of GSLs in myb29OE exhibited reduced plant growth (reduced size) and increased stress (purple leaf tissue). I quantified this potential tradeoff between plant health and GSL content using plantCV, an open source, python based image analysis tool. I expect that the time of day in which sulfur is provided will significantly affect growth, and that plant health will be reduced when GSLs are accumulated. One explanation for this would be due to alterations in sulfur pools; specifically, forcing sulfur flux towards specialized metabolism (GSLs) and away from primary metabolism. Understanding the importance of time of day application of sulfur could help farmers to utilize sulfur efficiently for crop management, while a better understanding of how GSLs affect plant physiology can help Brassica farmers increase the nutritive value and quality of their crops