Parent-of-Origin-Effect rough endosperm Mutants in Maize

Area of Science:

• Plant genetics
• Developmental biology
• Epigenetics

Background:

• Parent-of-origin effect loci exhibit non-Mendelian inheritance, with phenotypes determined by maternal or paternal alleles.
• In angiosperms, these effects stem from gametophyte development loci or imprinted genes crucial for seed development.
• Few parent-of-origin effect loci are identified in maize (Zea mays), despite known imprinted genes from transcriptomics.

Purpose of the Study:

• Screen maize rough endosperm (rgh) mutants for parent-of-origin effects using reciprocal crosses.
• Identify and characterize maternal rough endosperm (mre) and paternal rough endosperm (pre) mutants.
• Investigate the genetic and developmental basis of parent-of-origin effects in maize seed development.

Main Methods:

• Reciprocal crosses between inbred maize parents to screen for rough endosperm mutants.
• Identification of maternal (mre) and paternal (pre) rough endosperm mutants.
• Genetic mapping of mre loci and histological analysis of endosperm development.

Main Results:

• Six maternal (mre) and three paternal (pre) rough endosperm mutants were identified.
• Maternal inheritance of mre/+ seeds reduced grain fill with rough endosperm; pollen transmission of pre mutants caused rough endosperm and embryo lethality.
• Histological analysis revealed altered starch accumulation and basal endosperm transfer cell layer (BETL) development in mutants, with mre1 delaying BETL and starchy endosperm development, and mre2 and pre*-949 causing ectopic starchy endosperm differentiation.

Conclusions:

• Many parent-of-origin effect loci in maize exhibit incomplete penetrance of kernel phenotypes.
• A wide diversity of endosperm developmental roles exist for parent-of-origin effect loci in maize.
• The identified mre and pre mutants provide insights into the genetic control of seed development and parent-of-origin effects.