Identification of Differentially Expressed Genes in Semigametic Pima Cotton by Differential Display.

Haploid seed-producing semigamy in cotton is controlled by a single incompletely dominant gene ( Se). However, its molecular mechanism is currently poorly understood. In this study, the mRNA differential display (DD) was employed to compare gene expression between non-semigametic Pima S-1 ( Gossypium barbadense) and its naturally occurring semigametic mutant 57-4. Of the 70 DD cDNA fragments isolated from a total of 3,000 cDNA fragments, some exhibited semigamy-specific expression across anthers and/or ovules. Of the 61 cDNA fragments cloned and sequenced, nine showed high homology to genes encoding for α-tubulin, SPK1, Rab11, sucrose synthase, isocitrate lyase, phosphoethanolamine N-methyltransferase, phospholipase D, MADS 7, and WRKY 2. From cDNA-single-strand conformational polymorphism using primers designed from DD sequences, qualitative expression differences in six genes between the semigametic and non-semigametic genotypes were validated. However, a primer pair designed from an α-tubulin gene sequence yielded PCR products with quantitative difference in band intensity, which is linked to the semigamy gene at a recombination frequency of 0.316 in a (57-4 × Pima S-1) × Pima S-1 BC1F1 population. Its expression in the semigametic 57-4 anthers was suppressed by 2-fold as compared to that in Pima S-1 using a quantitative reverse transcription PCR analysis. This study identified several novel genes that were missed in prior microarray analysis, and their potential roles with regards to reproductive biology are discussed. [ABSTRACT FROM AUTHOR]