Isolation and characterization of high-mobility-group proteins from maize.

Area of Science:

• Plant molecular biology
• Chromatin structure and function
• Biochemistry

Background:

• High-mobility-group (HMG) proteins are crucial for chromatin organization and gene regulation in eukaryotes.
• Understanding tissue-specific HMG protein expression is key to deciphering differential gene activity in plants like maize.

Purpose of the Study:

• To purify and characterize chromosomal nonhistone high-mobility-group (HMG) proteins from maize endosperm and leaf tissues.
• To investigate tissue-specific variations in HMG protein profiles, phosphorylation, and DNA-binding properties.

Main Methods:

• Purification of HMG proteins from maize (Zea mays L. cv. A619) endosperm and leaf nuclei.
• Analysis of polypeptide patterns, in vitro phosphorylation using casein kinase II, and Western blotting.
• Gel filtration chromatography for determining HMG protein molecular state (monomers).
• Assessment of HMG protein binding to the 5' flanking region of a zein gene under varying conditions (temperature, salt, pH).

Main Results:

• Tissue-specific differences were observed in the polypeptide patterns of maize HMG proteins.
• In vitro phosphorylation assays revealed differential modification of HMG proteins by casein kinase II.
• Western blot analysis indicated distinct HMG protein profiles between endosperm and leaf tissues.
• Maize HMG proteins were confirmed to exist as monomers via gel filtration.
• The study quantified the binding capacity of HMG proteins to a zein gene promoter, revealing sensitivities to temperature, salt concentration, and pH.

Conclusions:

• Maize HMG proteins exhibit tissue-specific characteristics, suggesting specialized roles in gene regulation in different plant tissues.
• The characterized HMG proteins are monomers and their DNA-binding activity is modulated by environmental factors, providing insights into their dynamic function in vivo.