Changes in fruit firmness, cell wall composition and transcriptional profile in the yellow fruited tomato 1 (yft1) mutant.

Fruit firmness is an important trait in tomato (Solanum lycopersicum), associated with shelf life and economic value; however, the precise mechanism determining fruit softening remains elusive. A yellow fruit tomato 1(yft1) mutant, harbors a genetic lesion in the YFT1 gene, and has significantly firmer fruit than those of the cv. M82 wild type at a red ripe stage, 54 dpa (days post anthesis). When softening was further dissected, it was found that the yft1 firm fruit phenotype correlated with a difference in cellulose, hemicellulose and pectin deposition in the primary cell wall (PCW) compared to cv.M82. Alterations in the structure of the pericarp cells, chemical components, hydrolase activities and expression of genes encoding these hydrolases, were all hypothesized to be a result of the loss of YFT1 function. This was further affirmed by RNA-seq analysis, where a total of 183 differentially expressed genes (DEGs, 50/133 down/up-regulated) were identified between yft1 and cv.M82. These DEGs were mainly annotated as participating in ethylene and auxin related signal transduction, sugar metabolism and photosynthesis. This study provides new insights into mechanism underlying the control of fruit softening.