Comparative analysis of BiP gene expression in maize endosperm

Area of Science:

• Molecular Biology
• Plant Science
• Genetics

Background:

• Binding protein (BiP) is an endoplasmic reticulum-localized molecular chaperone belonging to the conserved HSP70 family.
• BiP plays a crucial role in protein folding and quality control within the cell.

Purpose of the Study:

• To isolate and characterize maize BiP cDNA clones expressed in immature kernels.
• To investigate the expression patterns and genomic complexity of maize BiP genes, particularly in relation to endosperm development and protein folding stress.

Main Methods:

• Isolation and characterization of BiP cDNA clones from maize.
• RNA gel blot analysis to study gene expression.
• Southern blot analysis to assess genomic complexity.
• Sequence comparison of predicted amino acid sequences.

Main Results:

• Two distinct BiP cDNA clones with high sequence similarity were identified, mapping to unlinked loci in the maize genome.
• Expression of both BiP genes was upregulated in maize mutants (floury-2, Mucronate, Defective endosperm-B30) exhibiting abnormal endosperm storage proteins.
• Increased BiP RNA levels were also observed in cells treated with protein-folding inhibitors (azetidine-2-carboxylic acid and tunicamycin).
• Southern blot analysis indicated the presence of a complex maize BiP multigene family.

Conclusions:

• The BiP genes expressed in maize endosperm are likely coordinately regulated.
• These findings suggest a role for BiP in managing protein folding stress during maize kernel development.
• Maize possesses a complex multigene family for BiP, indicating sophisticated regulation of this chaperone system.