Abstract
Plant trait diversity is known to influence population yield, but the scale at which this happens remains unknown: divergent individuals might change yields of immediate neighbors (neighbor scale) or of plants across a population (population scale). We use Nicotiana attenuata plants silenced in mitogen-activated protein kinase 4 (irMPK4) - with low water-use efficiency (WUE) - to study the scale at which water-use traits alter intraspecific population yields. In the field and glasshouse, we observed overyielding in populations with low percentages of irMPK4 plants, unrelated to water-use phenotypes. Paired-plant experiments excluded the occurrence of overyielding effects at the neighbor scale. Experimentally altering field arbuscular mycorrhizal fungal associations by silencing the Sym-pathway gene NaCCaMK did not affect reproductive overyielding, implicating an effect independent of belowground AMF interactions. Additionally, micro-grafting experiments revealed dependence on shoot-expressed MPK4 for N. attenuata to vary its yield per neighbor presence. We find that variation in a single gene, MPK4, is responsible for population overyielding through a mechanism, independent of irMPK4's WUE phenotype, at the aboveground, population scale.
Highlights
Plant trait diversity is known to increase the productivity and stability of plant populations (Cardinale et al, 2012; Isbell et al, 2017; Isbell et al, 2015; Liang et al, 2016; Loreau and de Mazancourt, 2013)
N. attenuata plants silenced in the expression of MITOGEN-ACTIVATED PROTEIN KINASE 4 (MPK4) have a low water-use efficiency (WUE) phenotype in comparison to empty-vector (EV) control plants in the glasshouse (Figure 2A)
As silencing the expression of NaCCaMK disconnects plants from arbuscular mycorrhizal fungal (AMF) networks (Groten et al, 2015), we crossed isogenetic, homozygous irCCaMK plants with homozygous EV and in the expression of MPK4 (irMPK4) lines to generate hemizygous EV x irCCaMK (EVxCC) and irMPK4 x irCCaMK (MPxCC) lines (Figure 2B), which were used for field experiments
Summary
Plant trait diversity is known to increase the productivity and stability of plant populations (Cardinale et al, 2012; Isbell et al, 2017; Isbell et al, 2015; Liang et al, 2016; Loreau and de Mazancourt, 2013). These effects may be produced from single gene variation among individuals: previously, wheat populations comprising of two lines varied only in their resistance to powdery mildew through single-gene modifications outperformed monoculture populations, even when the monocultures were comprised of resistant individuals (Zeller et al, 2012).
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