Properties of proteins and the glassy matrix in maturation-defective mutant seeds ofArabidopsis thaliana
In situFourier transform infrared microspectroscopy was used to study the heat stability of proteins and hydrogen bonding interactions in dry maturation-defective mutant seeds ofArabidopsis thaliana. α-Helical, turn and -sheet conformations were the major protein secondary structures in all of these seeds. On heating, intermolecular extended -sheet structures, typical of protein denaturation, were formed in abscisic acid-insensitive (abi3) and leafy cotyledon (lec) mutant seeds. Proteins in dry wild-type seeds did not denature up to 150°C, but those in dry desiccation-sensitive,lec1–1,lec1–3andabi3–5seeds did at 68, 89 and 87°C, respectively. In the desiccation-tolerantabi3–7andabi3–1seeds, denaturation commenced above 120 and 135°C, respectively. Seeds of theaba1–1 abi3–1double mutant showed signs of denaturation already upon drying. The molecular packing in the seeds was studied by observing the shift in the position of the OH-stretching vibration band with temperature. The maximal rate of change of this band with temperature was much higher in the desiccation-sensitiveabi3–5,aba1–1 abi3–1,lec1–1, andlec1–3mutant seeds than in the desiccation-tolerant wild-type,abi3–1,abi3–7, andlec2–1seeds. We interpret this to mean that the molecular packing density is higher in dry desiccation-tolerant than in dry desiccation-sensitive seeds, which is associated with a higher or lower protein denaturation temperature, respectively. The results are discussed in relation to the physiological and biochemical characteristics of these mutant seeds.
Document Type: Original Article
Affiliations: 1: Laboratory of Plant Physiology, Department of Biomolecular Sciences, Wageningen Agricultural University, Arboretumlaan 4, NL-6703 BD Wageningen, The Netherlands, and 2: Laboratory of Genetics, Department of Biomolecular Sciences, Wageningen Agricultural University, Dreijenlaan 2, NL-6703 HA Wageningen, The Netherlands
Publication date: October 1, 1998