Sorting out theLeMANs: endo-β-mannanase genes and their encoded proteins in tomato

Endo-β-mannanase (EC 3.2.1.78) is involved in the hydrolysis of mannan-type polysaccharides that are present in plant cell walls, especially those of the seed endosperm. The genes encoding the endo-β-mannanases have been studied extensively in tomato (Solanum lycopersicum), and five genes (LeMAN1,LeMAN2,LeMAN3,LeMAN4andLeMAN5) and/or their products have been isolated and characterized.LeMAN1,LeMAN2andLeMAN3are expressed in tomato seeds,LeMAN4in the fruit andLeMAN5in the flower.LeMAN5andLeMAN2are now considered to be the same gene, and the former is re-designated asLeMAN2*. Transcripts ofLeMANs1, 2and3are detected only in the endosperm of tomato seeds, and their synthesis is promoted by gibberellic acid.LeMAN4, in the fruit, occurs asLeMAN4aandLeMAN4igenes that encode an active or inactive form of endo-β-mannanase, respectively.LeMAN1–4 enzymes encoded by these genes share 80% similarity in amino acid sequence. In tomato, the leucine amino acid present near to the C-terminus of the endo-β-mannanase is the most important for achieving full activity of the enzyme.