Biochemical features of maize tissues with different capacities to regenerate plants

Metabolic profiling using GC-MS and LC-MS analyses of soluble metabolites and cell wall bound phenolic compounds from maize calluses of different morphogenic competence revealed a number of biochemical characteristics that distinguish tissues with high plant regeneration ability from tissues that cannot efficiently regenerate plants in vitro. Maize cultures of different ages from H99 (compact type I callus) and HiII (friable type II callus) were divided into two different samples: regenerable (R) and non-regenerable (NR) based on known morphologies. Tissues from both genotypes with high morphogenic potential had higher asparagine and aspartate and indole-3-butenol concentrations, decreased sugar and DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) concentrations, low levels of 4-aminobutyric acid ( GABA) and chlorogenic acid and lower levels of feruloyl- and sinapoyl glucosides compared to NR tissues. The ether bound cell wall phenolics of tissues with high regeneration potential had higher levels of the predominant G (guaiacyl) units and lower levels of H (p-hydroxyphenyl) and S (syringyl) units and higher ferulic acid/coumaric acid and ferulic acid/diferulic acid ratios. The same trends were found with the ester-bound phenolics of HiII, however, there were only small differences between the H99 R and NR tissues. Concentrations of the major sugars, organic acids, amino acids and soluble aromatic compounds tended to increase as the time after culture initiation increased. The results show that there are differences in general metabolism, phenolic secondary compounds and cell wall composition between R and NR cell types.