IMPACT OF CHLOROPHYLL-RETENTION MUTATIONS, D1D2 AND CYT-G1, DURING EMBRYOGENY IN SOYBEAN

The ultrastructural, physiological, and molecular changes in developin g and mature seeds were monitored in a control line (Glycine max [L.] Merr., cv Clark) that exhibited seed degreening and two mutant lines ( d1d2 and cyt-G1) that retained chlorophyll upon seed maturation. Ultra structural studies showed that the control line had no internal membra nes, whereas stacked thylakoid membranes were detected in the green se ed from the mutant lines. Pigment analyses indicated that total chloro phyll was lowest in the mature seeds of the control line. Mature d1d2 and cyt-G1 seed had elevated Chl a and Chl b levels, respectively. In both control and mutant lines, Lhcb1, Lhcb2 and RbcS mRNAs were abunda nt in embryos prior to cotyledon filling, declined after the onset of storage protein accumulation, and were barely detectable or undetectab le in all later stages of seed development. Therefore, the chlorophyll -retention phenotype must be a result of the alteration of a process t hat occurs after translation of photosynthesis-related mRNAs to stabil ize apoprotein and pigment levels. Furthermore, different elements con trolling either the synthesis or turnover of Chl a and Chl b must be i mpaired in the d1d2 and cyt-G1 lines. No reproducible differences in t otal leaf, embryonic, and chloroplast protein profiles and plastid DNA s could be correlated with the mutations that induced chlorophyll rete ntion.