Maize Genetics Cooperation Newsletter

maize gene review

Author: Alice Barkan, University of Oregon, Eugene, OR. USA 97403


Review: pending

Pub date: May 2009

Name: tha4 thylakoid assembly4

Synonyms: CL1403_-2a

Chromosome 1L bin 1.05
Genome Browser via cDNA AF145755 | 4877983
Gene Model GRMZM2G472651.

Function: chloroplast tat protein translocation pathway; pale green seedling lethal

image of

corn mutant

Summary: Thylakoid protein targeting: tat pathway. In E. coli, the pathway has 3 protein components: tatA, tatB and tatC. tha4 is the ortholog of bacterial tatA. A tha4 mutant allele is slightly pale green and seedling lethal due to decreased levels of many thylakoid proteins.

Image: mutant leaf color depicted on a seedling leaf color scale

First Defining Report: Walker et al. 1999

Key Allele

tha4-m1::Mu1; Mu1 insertion 35 bp upstream of the start codon. Slightly pale green, seedling lethal phenotype with occasional green sectors.

Map Location

Maps to long arm of chromosome 1 with chromosome B-A translocations (Walker et al 1999).

Gene Product

THA4, a homolog of bacterial tatA, is localized to thylakoid membranes. The pea THA4 ortholog forms a tranlocating membrane channel (Dabney-Smith and Cline 2009). The tat protein translocation pathway is trans-membrane, pH-gradient dependent, and SecA independent. In bacteria, it involves three protein components: tatA, tatB and tatC. A tatC component has not yet been defined in maize.

Related loci

hcf106, ortholog of the bacterial tatB component.


Dabney-Smith C, Cline K (2009) Clustering of C-terminal stromal domains of Tha4 homo-oligomers during translocation by the Tat protein transport system. Mol Biol Cell 20:2060-9. PUBMED

Walker MB, Roy LM, ColemanE, Voelker R, Barkan A (1999) The maize tha4 gene functions in Sec-independent protein transport in chloroplasts and is related to hcf106, tatA, and tatB. J Cell Biol 147: 267-276. PUBMED

Links: MGDB: tha4 NCBI: tha4 UniProt: Q9XFJ8