Abstract
Maize is the highest yielding cereal crop grown worldwide for grain or silage. Here, we show that modulating the expression of the maize PLASTOCHRON1 (ZmPLA1) gene, encoding a cytochrome P450 (CYP78A1), results in increased organ growth, seedling vigour, stover biomass and seed yield. The engineered trait is robust as it improves yield in an inbred as well as in a panel of hybrids, at several locations and over multiple seasons in the field. Transcriptome studies, hormone measurements and the expression of the auxin responsive DR5rev:mRFPer marker suggest that PLA1 may function through an increase in auxin. Detailed analysis of growth over time demonstrates that PLA1 stimulates the duration of leaf elongation by maintaining dividing cells in a proliferative, undifferentiated state for a longer period of time. The prolonged duration of growth also compensates for growth rate reduction caused by abiotic stresses.
Highlights
Maize is the highest yielding cereal crop grown worldwide for grain or silage
PLASTOCHRON1 (PLA1) that belongs to the same class of CYP78A as KLUH affects the timing of leaf initiation and vegetative growth[22]
The two well-characterized members of the CYTOCHROME P450 78A family that were described to date, KLUH and PLA1, affect plastochron and vegetative growth[22,23,24]
Summary
We show that modulating the expression of the maize PLASTOCHRON1 (ZmPLA1) gene, encoding a cytochrome P450 (CYP78A1), results in increased organ growth, seedling vigour, stover biomass and seed yield. More metric tons of maize are produced annually than any other cereal crop and this is largely due to improvements in stover biomass and seed yield. These improvements were driven by modulation of several molecular mechanisms including transcriptional regulation[1], photosynthesis[2], hormone signalling[3] and carbon metabolism[4]. Using the maize leaf as a reporter, we demonstrated that localized ectopic expression of ZmPLA1 resulted in an increased duration of the maximal growth rate during steady state growth. Transcriptome studies, hormone measurements and the DR5rev:mRFP marker line suggest auxin contributes to this compensatory growth mechanism
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