Determining the scale at which variation in a single gene changes population yields

Area of Science:

• Ecology
• Genetics
• Plant Biology

Background:

• Plant trait diversity influences population yield, but the scale of this effect is not well understood.
• Intraspecific interactions can modify individual and population performance, but the underlying genetic and ecological mechanisms are complex.

Purpose of the Study:

• To investigate the scale at which plant trait variation, specifically water-use efficiency (WUE), affects intraspecific population yields.
• To determine the genetic basis and interaction scale of overyielding in *Nicotiana attenuata*.

Main Methods:

• Utilized *Nicotiana attenuata* plants with silenced mitogen-activated protein kinase 4 (irMPK4) to assess WUE and population yield.
• Conducted field and glasshouse experiments, including paired-plant and micro-grafting studies.
• Investigated the role of arbuscular mycorrhizal fungal (AMF) associations by silencing the Sym-pathway gene *NaCCaMK*.

Main Results:

• Overyielding was observed in populations with low percentages of irMPK4 plants, independent of WUE phenotypes.
• Neighbor-scale overyielding effects were excluded through paired-plant experiments.
• Silencing *NaCCaMK* did not affect reproductive overyielding, suggesting an AMF-independent mechanism.
• Micro-grafting revealed that shoot-expressed *MPK4* is crucial for yield variation in response to neighbor presence.

Conclusions:

• Variation in the *MPK4* gene drives population overyielding in *Nicotiana attenuata*.
• The mechanism is independent of the irMPK4 WUE phenotype and operates at the population scale, primarily through aboveground interactions.
• Plant trait diversity, modulated by specific genes like *MPK4*, can significantly impact population-level outcomes.