Analysis Of Pigment-Protein Complexes In Mungbean Testa

We examined the chlorophyll (Chl) content, Chl a/b ratio, Chl biosynthetic capacity, and pigment-protein complexes of dry mungbean (Vigna mdintn L.) testa. The dry testa contains 12% as much Chl as does the dry leaf. The Chl a/b ratio of the testa is less than 1/1, that of leaf is approximately 3/1, similar to that usually found in higher plants. Using the Thornber electrophoretic system, mungbean testa was found to lack pigment-protein complex CPI, and using the MARS (Markwell and Reinman System) fractionation system, the testa was found to be totally deficient in pigment-protein complexes A1, AB1, and AB2. Among these complexes, CPI and A1 are derived from PSI, and AB1 and AB2 from light-harvesting chlorophyll a/b-binding protein complexes of PSII (LHCII). Supplementation test with precursor delta-aminolevulinic acid (ALA) shows that mungbean testa is unable to synthesize Chl. Darkness- or dim-light-treatment for 24 h seems to delay the degradation of Chl or pigment-protein complexes in the mungbean testa, whereas intense light accelerates it. We propose that the pigment-protein complexes CPII, A2, and AB3 of mungbean testa are the residual components of testa development and protect the embryo from incident light.