Plant Molecular Biology

, Volume 67, Issue 3, pp 215–229

A member of the maize isopentenyl transferase gene family, Zea mays isopentenyl transferase 2 (ZmIPT2), encodes a cytokinin biosynthetic enzyme expressed during kernel development

Cytokinin biosynthesis in maize
  • Norbert Brugière
  • Sabrina Humbert
  • Nancy Rizzo
  • Jennifer Bohn
  • Jeffrey E. Habben
Article

DOI: 10.1007/s11103-008-9312-x

Cite this article as:
Brugière, N., Humbert, S., Rizzo, N. et al. Plant Mol Biol (2008) 67: 215. doi:10.1007/s11103-008-9312-x

Abstract

Cytokinins (CKs) are plant hormones that regulate a large number of processes associated with plant growth and development such as induction of stomata opening, delayed senescence, suppression of auxin-induced apical dominance, signaling of nitrogen availability, differentiation of plastids and control of sink strength. In maize, CKs are thought to play an important role in establishing seed size and increasing seed set under normal and unfavorable environmental conditions therefore influencing yield. In recent years, the discovery of isopentenyl transferase (IPT) genes in plants has shed light on the CK biosynthesis pathway in plants. In an effort to increase our understanding of the role played by CKs in maize development and sink-strength, we identified several putative IPT genes using a bioinformatics approach. We focused our attention on one gene in particular, ZmIPT2, because of its strong expression in developing kernels. The expression of the gene and its product overlays the change in CK levels in developing kernels suggesting a major role in CK biosynthesis for kernel development. We demonstrate that at 8–10 days after pollination (DAP) the endosperm and especially the basal transfer cell layer (BETL) is a major site of ZmIPT2 expression, and that this expression persists in the BETL and the developing embryo into later kernel development stages. We show that ectopic expression of ZmIPT2 in calli and in planta created phenotypes consistent with CK overproduction. We also show that ZmIPT2 preferentially uses ADP and ATP over AMP as the substrates for dimethylallyl diphosphate (DMAPP) IPT activity. The expression pattern of ZmIPT2 in the BETL, endosperm and embryo during kernel development will be discussed with an emphasis on the suggested role of CKs in determining sink-strength and grain production in crop plants.

Keywords

Cytokinin biosynthesisIsopentenyl transferaseMaizeZmIPT2

Abbreviations

BETL

Basal endosperm transfer layer

cis-Z

cis-zeatin

IPT

Isopentenyl transferase

iPAR

Isopentenyl adenosine

iPMP

Isopentenyl adenosine mono-phosphate

iPTP

Isopentenyl adenosine tri-phosphate

PPCBE

Pedicel/placental chalazal/basal endosperm

t-Z

trans-zeatin

ZmIPT2

Zea mays isopentenyl transferase 2

ZR

Zeatin riboside

Supplementary material

11103_2008_9312_MOESM1_ESM.xls (22 kb)
Supplemental Table 1SZmIPT Genbank accession numbers and corresponding MAGI and AZM contigs (XLS 22 kb)
11103_2008_9312_MOESM2_ESM.ppt (924 kb)
Supplemental Fig. 1SSouthern blot using B73 and Mo17 genomic DNA and ZmIPT2 32P-dCTP as a probe. Only one band could be detected after hybridization when HindIII (H), EcoRI (E) or EcoRV (V) restriction enzymes were used suggesting that the gene is present at a single copy per haploid genome (PPT 925 kb)
11103_2008_9312_MOESM3_ESM.ppt (62 kb)
Supplemental Fig. 2SChromosomic location of ZmIPT2 determined by PCR using oat-maize addition lines. ZmIPT2 was only found in the DNA of the oat-maize addition line containing maize chromosome 2 (OMAL 2). Position was further determined as chromosome 2 bin 4 using BAC clones and a proprietary genetic physical map (PPT 63 kb)

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Norbert Brugière
    • 1
  • Sabrina Humbert
    • 1
    • 2
  • Nancy Rizzo
    • 3
  • Jennifer Bohn
    • 1
  • Jeffrey E. Habben
    • 1
  1. 1.Discovery Group/Agronomic TraitsPioneer Hi-Bred International, Inc., A DuPont BusinessJohnstonUSA
  2. 2.Department of Molecular and Cellular Biology, Science ComplexUniversity of GuelphGuelphCanada
  3. 3.Analytical and Genomics TechnologiesWilmingtonUSA