Native alleles at lhcb6 shape photosynthetic efficiency and early growth in maize

Maize is a globally important staple crop, providing food, animal feed, and industrial raw materials. Its extensive native diversity can be utilized to broaden the genetic basis for quantitative trait improvement and advance our understanding of the genotype-phenotype relationships underlying complex trait variation. In a forward genetic approach, we dissect a locus on chromosome 10 with major effects on Photosystem II (PSII) maximum quantum efficiency (Fv/Fm), non-photochemical quenching (NPQ) and biomass accumulation during early growth stages. Integrating molecular and physiological information we show that allelic variation at the gene encoding LIGHT HARVESTING CHLOROPHYLL A/B BINDING PROTEIN6 (LHCB6 also known as CP24), a component of the PSII light-harvesting complex (LHCII) antenna, underlies this locus. We demonstrate that the allelic variation results from a hAT transposon insertion at lhcb6 and is associated with decreased accumulation of the LHCII antenna components LHCB6 and LHCB3. Based on proteomic analyses we propose candidate genes that partially compensate for the unfavorable early growth effects caused by impaired LHCII antenna assembly. Our work provides novel insights into the function of lhcb6 in the C4 crop maize and demonstrates the value of natural variation for the understanding and genetic improvement of complex photosynthetic processes.