DELLA genes restrict inflorescence meristem function independently of plant height

Abstract

DELLA proteins associate with transcription factors to control plant growth in response to gibberellin1. Semi-dwarf DELLA mutants with improved harvest index and decreased lodging greatly improved global food security during the ‘green revolution’ in the 1960–1970s2. However, DELLA mutants are pleiotropic and the developmental basis for their effects on plant architecture remains poorly understood. Here, we show that DELLA proteins have genetically separable roles in controlling stem growth and the size of the inflorescence meristem, where flowers initiate. Quantitative three-dimensional image analysis, combined with a genome-wide screen for DELLA-bound loci in the inflorescence tip, revealed that DELLAs limit meristem size in Arabidopsis by directly upregulating the cell-cycle inhibitor KRP2 in the underlying rib meristem, without affecting the canonical WUSCHEL-CLAVATA meristem size regulators3. Mutation of KRP2 in a DELLA semi-dwarf background restored meristem size, but not stem growth, and accelerated flower production. In barley, secondary mutations in the DELLA gain-of-function mutant Sln1d 4 also uncoupled meristem and inflorescence size from plant height. Our work reveals an unexpected and conserved role for DELLA genes in controlling shoot meristem function and suggests how dissection of pleiotropic DELLA functions could unlock further yield gains in semi-dwarf mutants.

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Fig. 1: DELLA proteins control inflorescence meristem size.
Fig. 2: The cell-cycle inhibitor KRP2 is a direct DELLA target in the shoot apex.
Fig. 3: KRP2 mediates DELLA control of meristem size and bud production but not stem elongation.
Fig. 4: DELLA control of meristem size is conserved and correlates with inflorescence size in barley.

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Acknowledgements

We thank P. Chandler, L. Østergaard, T.-P. Sun, N. Harberd, P. Doerner, V. Reddy, Miguel Á. Pérez Amador and the European Arabidopsis Stock Centre for plasmids and seeds, G. Calder for advice with confocal microscopy and B. Shi for help with vibratome sections. The work was supported by BBSRC grants BB/J007056/1, BB/J004588/1 and BB/M003825/1, and by a grant from the Ministerio de Educación, Cultura y Deporte, Spain (EX-2010-0491) to A.S.-M.

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Conceptualization, A.S.-M., S.Bo. and R.S.; investigation, A.S.-M., S.Be., M.B., S.Bo. and K.S.; software, R.S.; formal analysis and data curation, A.S.-M. and R.S.; writing — original draft, A.S.-M. and R.S.; writing — review and editing, A.S.-M., S.Be., M.B., S.Bo., K.S. and R.S.; funding acquisition, R.S. and A.S.-M.; supervision, R.S.

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Correspondence to Robert Sablowski.

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Supplementary Information

Supplementary Methods, Supplementary References, Supplementary Figures 1-6, Supplementary Table legends.

Table 1

High-confidence targets of RGAp:GFP-rga_17 identified by ChIP-seq in inflorescence apices.

Table 2

Manually annotated functional categories of selected RGAp:GFP-rgaD17 target genes identified by ChIP-seq in inflorescence apices.

Table 3

Source images and processing steps for data presented in each figure.

Table 4

Imaging data — filtering parameters, source data and statistical analysis for each figure.

Table 5

ChIP–PCR source data and statistics (related to Fig. 3c).

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Serrano-Mislata, A., Bencivenga, S., Bush, M. et al. DELLA genes restrict inflorescence meristem function independently of plant height. Nature Plants 3, 749–754 (2017). https://doi.org/10.1038/s41477-017-0003-y

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