A customized gene expression microarray reveals that the brittle stem phenotype fs2 of barley is attributable to a retroelement in the HvCesA4 cellulose synthase gene.
The barley (Hordeum vulgare) brittle stem mutants, fs2, designated X054 and M245, have reduced levels of crystalline cellulose compared with their parental lines Ohichi and Shiroseto. A custom-designed microarray, based on long oligonucleotide technology and including genes involved in cell wall metabolism, revealed that transcript levels of very few genes were altered in the elongation zone of stem internodes, but these included a marked decrease in mRNA for the HvCesA4 cellulose synthase gene of both mutants. In contrast, the abundance of several hundred transcripts changed in the upper, maturation zones of stem internodes, which presumably reflected pleiotropic responses to a weakened cell wall that resulted from the primary genetic lesion. Sequencing of the HvCesA4 genes revealed the presence of a 964-bp solo long terminal repeat of a Copia-like retroelement in the first intron of the HvCesA4 genes of both mutant lines. The retroelement appears to interfere with transcription of the HvCesA4 gene or with processing of the mRNA, and this is likely to account for the lower crystalline cellulose content and lower stem strength of the mutants. The HvCesA4 gene maps to a position on chromosome 1H of barley that coincides with the previously reported position of fs2.
Australian Centre for Plant Functional Genomics, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia.
Rachel A
RA
Burton
Gang
G
Ma
Ute
U
Baumann
Andrew J
AJ
Harvey
Neil J
NJ
Shirley
Jillian
J
Taylor
Filomena
F
Pettolino
Antony
A
Bacic
Mary
M
Beatty
Carl R
CR
Simmons
Kanwarpal S
KS
Dhugga
J Antoni
JA
Rafalski
Scott V
SV
Tingey
Geoffrey B
GB
Fincher
D002473:Cell Wall / Q000737:chemistry; D002482:Cellulose / Q000032:analysis; D002874:Chromosome Mapping; D020869:Gene Expression Profiling; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D001467:Hordeum / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D018626:Retroelements
D010940:Plant Proteins; D018749:RNA, Plant; D018626:Retroelements; D002482:Cellulose; D005964:Glucosyltransferases; C478648:cellulose synthase