Cloning And Analysis Of A Floral Organ Specific MADS-box Gene (GhMADS-1) From Cotton (Gossypium Hirsutum L.)

As an important transcription factor, MADS-box protein plays an important role in various cellular processes, especially in regulation of floral organ development. The genes related to this identity are conserved MADS-box genes whose name initially came from the first letter of MCMl(from yeast), AGAMOUS (from Arabidopsis), DEFICIENS (bom Antirrhinum) and S/ZF(from human). The MADS region linked specifically to the coalescent site of target gene and formed a homogenous or heterogenous dimer to regulate it, which can make different kinds of-floral organs for many flowering plants. So they are important factors to control the development of floral organs and to make homeotic transformations. It is very useful to clone and analyze the floral organ identity genes in order to understand the molecular model of plant floral organ development and to improve the flower varieties using gene engineering.Cotton is an important economic plant because of its fiber and its floral organ is also very specific. The floral organ mutant (CHV1) found by our lab is a precious material for us to understand the development of floral organs of cotton. Using the land cotton xuzhou 142 and the mutant CHV1 as the materials, the coding region of a cotton MADS-box protein was obtained by RT-PCR from buds of cotton based on the contig analysis and the cotton ovule & fiber EST database. Sequence comparison and functional analysis have been made and the results are as follows: 1. Cloning of GhMADS-l:The cloned fragment of 715 bp contains an open reading frame of 711 bp, coding a polypeptide of 236 amino acids designated as GhMADS-l. It has been submitted to the GenBank database and the accession number is AF538965.2. Homologous analysis of GhMADS-1:Sequence analysis shows that the deduced GhMADS-1 protein was highly homologous to the AGL2-typed-MADS proteins of Vitis vinifera, Nicotiana sylvestris, Petunia hybrida, Arabidopsis thaliana and Antirrhinum majus. Phylogenetic analysis also indicates that GhMADS-1 belongs to the novel MADS box protein type_AGL2.3. Structure analysis of GhMADS-1:The GhMADS-1 is a classical MADS-box gene of plant MIKC-type. The MADS box (l-62aa) is in the N-end and the K box (90-160aa) in the middle. The I region (intervening region) is between the MADS box and the K box which encodes a keratin-like protein structure and it is very important to make heterogenous dimer of two MADS box genes. The C-end is a non-conserved region and its function is not very clear.4. RT-PCR expression analysis of GhMADS-1:RT-PCR expression analysis shows that GhMADS-1 gene expressed in petal, anther, ovule and fiber, but not in root, stem, leaf, bract and sepal. The strongest expression of GhMADS-1 gene was detected in petals, but not in the floral buds of a somatic mutant(CHVl). It was proposed that GhMADS-1 gene would be crucial for the development of cotton floral organs and the reproductive organ development.5. The relationship between GhMADS-1 and CHV1:According to the function of AGL2 subfamily and the RT-PCR analysis of GhMADS-1 in CHV1, GhMADS-1 gene is not expressed in CHV1 shows that the gene is probably related to the construction of CHV1. To make clear the molecular mechanism of floral organ development of cotton, the continous research is ongoing.