GbEXPATR, a species-specific expansin, enhances cotton fibre elongation through cell wall restructuring.
Cotton provides us the most important natural fibre. High fibre quality is the major goal of cotton breeding, and introducing genes conferring longer, finer and stronger fibre from Gossypium barbadense to Gossypium hirsutum is an important breeding strategy. We previously analysed the G. barbadense fibre development mechanism by gene expression profiling and found two homoeologous fibre-specific α-expansins from G. barbadense, GbEXPA2 and GbEXPATR. GbEXPA2 (from the DT genome) is a classical α-expansin, while its homoeolog, GbEXPATR (AT genome), encodes a truncated protein lacking the normal C-terminal polysaccharide-binding domain of other α-expansins and is specifically expressed in G. barbadense. Silencing EXPA in G. hirsutum induced shorter fibres with thicker cell walls. GbEXPA2 overexpression in G. hirsutum had no effect on mature fibre length, but produced fibres with a slightly thicker wall and increased crystalline cellulose content. Interestingly, GbEXPATR overexpression resulted in longer, finer and stronger fibres coupled with significantly thinner cell walls. The longer and thinner fibre was associated with lower expression of a number of secondary wall-associated genes, especially chitinase-like genes, and walls with lower cellulose levels but higher noncellulosic polysaccharides which advocated that a delay in the transition to secondary wall synthesis might be responsible for better fibre. In conclusion, we propose that α-expansins play a critical role in fibre development by loosening the cell wall; furthermore, a truncated form, GbEXPATR, has a more dramatic effect through reorganizing secondary wall synthesis and metabolism and should be a candidate gene for developing G. hirsutum cultivars with superior fibre quality.
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Yang
Y
Li
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Lili
L
Tu
Commonwealth Scientific and Industrial Research Organization (CSIRO), Plant Industry, Canberra, ACT, Australia.
Filomena A
FA
Pettolino
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Shengmei
S
Ji
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Juan
J
Hao
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Daojun
D
Yuan
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Fenglin
F
Deng
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Jiafu
J
Tan
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Haiyan
H
Hu
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Qing
Q
Wang
Commonwealth Scientific and Industrial Research Organization (CSIRO), Plant Industry, Canberra, ACT, Australia.
Danny J
DJ
Llewellyn
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, China.
Xianlong
X
Zhang
D001483:Base Sequence; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D032561:Cotton Fiber; D003433:Crosses, Genetic; D015536:Down-Regulation / Q000235:genetics; D017343:Genes, Plant; D005816:Genetic Complementation Test; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D000072417:Protein Domains; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D010940:Plant Proteins; C095825:expansin protein, plant
Gossypium barbadense (cotton); cell elongation; cotton fibre; secondary cell wall; truncated α-expansin