Responses of Primary Metabolites and Glucosinolates in Sulfur Deficient-Cabbage (Brassica rapa L. ssp. Pekinensis)

Abstract

Sulfur (S) is an essential mineral nutrient for plant growth and development and is a key component of many biological compounds. As S acquisition and assimilation have important roles in plant metabolism, S-deficient responses are closely involved in different plant constituents. In this study, we examined the effects of S deficiency on primary metabolism and glucosinolate (GSL) content in cabbage (Brassica rapa) plants. Soluble sugars such as glucose, fructose, galactose, and xylose, were up to 0.19-fold lower under S deficiency, and these changes were more pronounced with long-term (15 d) S deficiency. Significant increases in amino acids were observed in terms of glutamine (6.35-fold), glycine (20.54), serine (3.56), threonine (3.25), phenylalanine (4.07), β-alanine (7.88), and proline (4.58). S deficiency led to large accumulation of an indolyl GSL, 4-methoxyglucobrassicin, in both shoots (2.68 fold) and roots (5.99 fold). GSLs were positively correlated with the majority of primary metabolites in the shoots, but negative in the roots. Thus, at least in cabbage plants, the interplay between primary metabolism and GSLs appeared to be tissue-dependent, and the metabolic interaction between both metabolites should be elucidated.