Long-Term Mild Heat Causes Post-Mitotic Pollen Abortion Through a Local Effect on Flowers.

Area of Science:

• Plant reproductive biology
• Stress physiology
• Molecular genetics

Background:

• Increasing global heatwaves pose significant threats to crop reproductive success.
• Heat-induced male sterility in crops is primarily linked to pollen development issues, but the exact mechanism (direct vs. systemic effects) remains unclear.

Purpose of the Study:

• To investigate whether long-term mild heat (LTMH) affects crop reproduction directly on flowers or systemically through other plant tissues.
• To identify the critical developmental stages and molecular mechanisms underlying heat-induced pollen sterility in tomato.

Main Methods:

• Application of LTMH treatment locally to tomato flowers or whole plants.
• Cytological, transcriptomic, and biochemical analyses of pollen and anther tissues.
• Assessment of pollen viability at different developmental stages and anthesis.

Main Results:

• LTMH directly impacts tomato flowers, leading to reduced pollen viability, rather than acting systemically.
• The meiosis to early microspore stage of pollen development is most sensitive to LTMH; 3 days of exposure significantly reduces viability.
• Pollen development abnormalities were observed after pollen mitosis I, associated with tapetal endoplasmic reticulum (ER) stress, with minimal evidence of oxidative stress.

Conclusions:

• Heat stress directly affects flowers, causing pollen sterility, challenging crop reproductive success.
• The molecular and physiological responses to LTMH differ from those induced by severe heat shock, highlighting stage-specific sensitivities.