Maize mutants and variants altering developmental time and their heterochronic interactions

Area of Science:

• Plant developmental biology
• Genetics
• Evolutionary biology

Background:

• Plant development is regulated by distinct mechanisms controlling stage transitions and flowering time.
• Mutant analysis reveals genetic control over shoot and leaf stage transitions, with some genes encoding homeodomain proteins.
• Plant heterochronism, the study of altered developmental timing, is investigated using mutants like Hairy sheath frayed 1-O (Hsf1-O).

Purpose of the Study:

• To investigate the interaction between plant stage-transition mechanisms and time-to-flowering genetic backgrounds.
• To explore the morphological variations arising from altered developmental timing in plants.
• To understand how these variations might contribute to macroevolutionary processes.

Main Methods:

• Analysis of dominant mutants affecting shoot and leaf stage transitions.
• Characterization of the Hairy sheath frayed 1-O (Hsf1-O) mutant.
• Genetic analysis of maize (Zea mays) cultivars with varying flowering times.
• Construction and observation of heterochronic genotypes.

Main Results:

• Mutants in at least four genes retard shoot stage transitions, and mutants in at least seven genes affect leaf stage transitions.
• The Hsf1-O mutant exhibits simultaneous effects on both shoot and leaf development.
• Interactions between stage-transition mutants and flowering time backgrounds produce radical and unexpected phenotypes.
• Heterochronic genotypes reveal a spectrum of previously unrecognized morphological possibilities.

Conclusions:

• Two distinct genetic mechanisms regulate plant development: stage transitions and flowering time.
• Interplay between these mechanisms generates significant morphological variation.
• This variation provides a potential source for macroevolutionary change, challenging the need for special mutational theories.