Programmed cell death in soybean seed coats.

Area of Science:

• Plant Biology
• Biochemistry
• Molecular Biology

Background:

• The seed coat acts as a crucial interface between the seed's internal tissues and the environment.
• Programmed cell death (PCD) is known to occur during cowpea seed coat development, but its role in germinating seed coats is less understood.

Purpose of the Study:

• To investigate the biochemical aspects of programmed cell death (PCD) in germinating soybean seed coats.
• To identify proteolytic activities associated with PCD in the soybean seed coat during germination.

Main Methods:

• Analysis of protease activity profiles (in-gel and in-solution) in quiescent and germinating soybean seed coat extracts.
• Assay of caspase- and metacaspase-like cysteine protease activities.
• Assessment of the effect of a pancaspase inhibitor (z-VAD-CHO) on radicle length.
• Ultrastructural analysis of seed coat layers post-imbibition.
• Quantification of oligonucleosome fragments at various time points after imbibition.

Main Results:

• Complex patterns of caspase- and metacaspase-like cysteine protease activities were detected in germinating soybean seed coats.
• Trypsin inhibitors and reserve proteins were identified as potential substrates for these proteases.
• Inhibition of pancaspase activity (z-VAD-CHO) impacted radicle elongation.
• Ultrastructural studies revealed the absence of cell organelles in seed coat layers after imbibition.
• Oligonucleosome fragments, a marker of PCD, peaked at 72 hours after imbibition (HAI).

Conclusions:

• Biochemical hallmarks of programmed cell death (PCD) are present in the germinating soybean seed coat.
• The detected protease activities likely contribute to reserve protein mobilization and seed coat weakening during germination.