Assessment of Heat Stress on Arabidopsis Pollen-pistil Interactions

Rising global temperatures have a detrimental effect on crop yield by inhibiting the production of seeds and fruits. Essential to this yield is the delivery of sperm cells to ovules by pollen tubes (PT), a process highly vulnerable to heat stress (HS). To determine how various HS conditions impact pollen-pistil interactions, we developed an in vivo assay that effectively demonstrates the effects of HS on Arabidopsis PT growth. This assay shows how different stages of PT growth were affected; pollen germination, growth in the transmitting tract, emergence from the transmitting tract, and ovule targeting were all susceptible to HS. Furthermore, as temperature increased, pollen tube growth ceased progressively earlier in its journey toward the ovules. Thus, failure of pollen-pistil interactions could be one of the many reasons underlying the yield reduction in crops under heat stress.
Our assay offers the opportunity to test PTs with mutated cell wall components, signaling molecules, or key proteins for PT maintenance under HS. Moreover, complementation of PT mutants or the beneficial effects of ectopic expression or overexpression of pollen-expressed genes in overcoming HS can be visualized and assayed using this assay. It can also be used to conduct mutant screens that identify pollen tubes capable of overcoming HS, potentially resulting in increased fertilization and seed development under such conditions.