Properties of proteins and the glassy matrix in maturation-defective mutant seeds of Arabidopsis thaliana.
In situ Fourier transform infrared microspectroscopy was used to study the heat stability of proteins and hydrogen bonding interactions in dry maturation-defective mutant seeds of Arabidopsis thaliana. alpha-Helical, turn and beta-sheet conformations were the major protein secondary structures in all of these seeds. On heating, intermolecular extended beta-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 degrees C, but those in dry desiccation-sensitive, lec1-1, lec1-3 and abi3-5 seeds did at 68, 89 and 87 degrees C, respectively. In the desiccation-tolerant abi3-7 and abi3-1 seeds, denaturation commenced above 120 and 135 degrees C, respectively. Seeds of the aba1-1 abi3-1 double 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-sensitive abi3-5, aba1-1 abi3-1, lec1-1, and lec1-3 mutant seeds than in the desiccation-tolerant wild-type, abi3-1, abi3-7, and lec2-1 seeds. 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.
Wolkers
W F
WF
Department of Biomolecular Sciences, Wageningen Agricultural University, The Netherlands. Wim.Wolkers@algem.pf.wau.nl
Alberda
M
M
Koornneef
M
M
Léon-Kloosterziel
K M
KM
Hoekstra
F A
FA
D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics; D029681:Arabidopsis Proteins; D002241:Carbohydrates / Q000737:chemistry*; D005838:Genotype; D006358:Hot Temperature; D008055:Lipids / Q000737:chemistry; D009154:Mutation; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D012639:Seeds / Q000737:chemistry* / Q000235:genetics; D017550:Spectroscopy, Fourier Transform Infrared; D014157:Transcription Factors
C091601:ABI3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002241:Carbohydrates; D008055:Lipids; D010940:Plant Proteins; D014157:Transcription Factors