Maize Genetics Cooperation Newsletter

maize gene review

Author: George Chuck, Plant Gene Expression Laboratory, USDA ARS, Albany, CA 40179 USA


Review: pending

Pub date: Mar 2009

Name: ts6 tasselseed6/ ids1 indeterminate spikelet1

Synonyms: cl1812_1, pge18, pzd00069, rgo2, reversed germ orientation2, umc1009

Chromosome 1L bin 1.11
GENOME BROWSER via BAC c0240n18/AC211154

Function: infloresence branching, floral and spikelet meristem determinancy

image of corn mutant

Summary: The ts6/ids1 gene was originally cloned by homology to the barley APETALA2-like gene provided by David Laurie. Using reverse genetics, two Mutator transposon insertions into ts6/ids1 were isolated by Robert Meeley. These recessive knockout mutants display indeterminate spikelets (ids) with multiple florets, each of which is present in the axil of a lemma bract. Dominant mutant tassels are compact, pistillate to mixed and ears have irregular kernel placement. In dominant mutants, the ear develops only when the pistillate tassel is removed; the heterozygote has a well formed tassel with scattered silks and produces kernels in both the tassel and ear (Nickerson et al. 1955) Weak recessive alleles exhibit a reverse germ orientation (rgo) in the ear, attributed to development of only lower florets, rather than the usual development of only upper florets. ts6/ids1 is functionally redundant with sister of indeterminate spikelet1 (sid1), a closely related homologue. Double mutants have indeterminate spikelets, much like recessive ts6/ids1, but do not initiate any florets in the axils of lemmas. The ts6/ids1 gene is a target of the miR172 microRNA encoded by the tasselseed4 locus.

Image: a razorblade hand-section of an ts6-ids1-mum1 ear spikelet

First defining reports:  Nickerson 1955; Chuck et al. 1998.

Key Alleles

ts6-ids1-mum1 displays indeterminate spikelets (ids) with multiple florets, each of which is present in the axil of a lemma bract; Mu insertion into intron5 (Chuck et al 1998).

ts6-ids1-mum2 is similar to ts6-ids1-mum1, except more severe; Mu insertion at junction of intron 1 and exon 2 (Chuck et al. 1998).

ts6-ids1-Burr, a weak allele, showing a reversed germ orientation phenotype in the ear and a mild extra floret phenotype in the tassel (Jackson and Kaplinsky 2000; Kaplinsky and Freeling 2003).

Ts6 ears develop only when pistillate tassel is removed. The heterozygote has silks in the tassel, and kernels in both tassel and ear (Nickerson 1955).

Map Location

Mapped by phenotype scoring (Emerson 1940); by restriction length polymorphism RFLP probe p-pGC1 (aka pge18, Burr et al 1988); by simple sequence repeat SSR, p-umc1009 probe (Sharopova et al. 2002); and to physical B73 BAC FPC map by the overgo probe CL1812_1_ov (Gardiner et al. 2004; Wei et al. 2009)

Gene Product

Encodes an APETALA2-like transcription factor.


ts6/ids1 is ubiquitously expressed in all tissues, but is expressed at higher levels during the floral phase in inflorescence and floral meristems.

Related loci

ts4, encodes a micro RNA that targets ts6/ids1 (Chuck et al. 2007).

sid1, a duplicate locus, functionally redundant with its closely related homologue ts6/ids1 (Chuck et al. 2008).


Burr B, Burr FA, Thompson KH, Albertson MC, Stuber CW (1988) Gene mapping with recombinant inbreds in maize. Genetics 118:519-526. PUBMED

Chuck G, Meeley R, and Hake S (1998). Thecontrol of maize spikelet meristem fate by the APETALA2-like gene indeterminate spikelet1. Genes and Development 12:1145-1154. PUBMED

Chuck G, Meeley R, Irish E, Sakai H, Hake S. (2007) The maize tasselseed4 microRNA controls sex determination and meristem cell fate by targeting Tasselseed6/indeterminate spikelet1. Nat Genet. 39:1517-1521. PUBMED

Chuck G, Meeley R, Hake S. (2008) Floral meristem initiation and meristem cell fate are regulated by the maize AP2 genes ids1 and sid1. Development 135:3013-3019. PUBMED

Emerson RA (1940) Tassel-seed 3 and tassel-seed 6. MNL 14:16

Gardiner J, Schroeder S, Polacco ML, Sanchez-Villeda H, Fang Z, Morgante M, Landewe T, Fengler K, Useche F, Hanafey M, Tingey S, Chou H, Wing R, Soderlund C, Coe EH Jr (2004) Anchoring 9,371 maize expressed sequence tagged unigenes to the bacterial artificial chromosome contig map by two-dimensional overgo hybridization. Plant Physiol. 134:1317-1326. PUBMED

Jackson J, Kaplinsky N (2000) The reverse germ orientation2-VI mutation maps to chromosome 1L near Ts6 and shows allelism to ids1. MNL 74:72-73.

Kaplinsky N, Freeling M (2003) Combinatorial control of meristem identity in maize inflorescences. Development 130:1149-1158. PUBMED

Nickerson NH and Dale EE (1955) Tassel modifications in Zea mays Annals of the Missouri Botanical Garden 42:195-212.

Wei F et al 2009 submitted. FPC map

Links: MGDB  ts6/ids1 NCBI ts6/ids1 UniProt O65008