Validation of microarray expression of selected genes by RT-MLPA. A total of 10 differentially regulated genes were selected in the validation using reverse transcriptase-multiplex ligation dependent probe amplification (RT-MLPA). These genes included eight genes preferentially transcribed in wood with high stiffness (HS) and lower microfibril angle (LM): 1- cellulose synthase 3 (PrCesA3); 2- chitinase-like; 3- protective protein for beta-galactosidase (PPBG); 4- cinnamate 4-hydroxylase (C4H); 5- phytochrome; 6- PrCesA11; 7- CCoAOMT; 8- transmembrane serine protease 9 (TSP9), and two genes selected in wood with low stiffness (LS) and higher microfibril angle (HM), 9- FadR and 10- T12C24.1. Log-2 ratios (HS/LS) of gene expression were calculated, and the values > 0 and < 0 indicate genes preferentially accumulated in HS (LM) and LS (HM) wood, respectively. Error bars represent the standard deviation of the mean log-2 ratio.