Maize early endosperm growth and development: from fertilization through cell type differentiation

Area of Science:

• Plant biology
• Developmental biology
• Genetics

Background:

• Maize (Zea mays) endosperm is economically vital, yet its development is understudied compared to other cereals.
• Understanding maize endosperm development is crucial for crop improvement and food security.

Purpose of the Study:

• To provide detailed morphometric and cytological descriptions of early endosperm development in the sequenced maize inbred line B73.
• To compare endosperm growth patterns in B73 with four diverse Nested Association Mapping (NAM) founder lines.

Main Methods:

• Semithin sections of plastic-embedded kernels and confocal microscopy were used to describe B73 endosperm development over the first 12 days.
• Longitudinal sections were analyzed to compare endosperm length, thickness, and area.

Main Results:

• Four distinct stages of early endosperm development were identified: coenocytic, alveolation, partitioning, and differentiation.
• Synchronous nuclear divisions were observed in the coenocyte, and cellularization onset correlated with endosperm size.
• A novel cell type, the basal intermediate zone (BIZ), was identified. Early endosperm size varied between NAM founders, correlating with mature kernel size.

Conclusions:

• A B73-specific model for early endosperm growth was established, linking developmental events to endosperm size across different growing conditions.
• Maize endosperm exhibits a unique cellularization process involving alveolation and central vacuole partitioning, differing from Arabidopsis, barley, and rice.
• NAM analysis indicated that early endosperm size differences in maize lines may be linked to variations in cellularization timing.