Dr. Sir or Madame,
I am a senior biochemistry major at a small college in Kentucky and I have a question about endosperm color for you. I am giving a presentation on paramutation this week for my senior seminar and am focusing on the anthocyanin inhibition resulting from paramutation at the r, pl, and especially b loci. I feel I have a very good grasp on the whole concept, but I am having one significant problem. At the r locus when paramutation occurs the endosperm pigmentation is inhibited by a 10 fold reduction in the transcription of the r (which codes for a transcription activator for an enzyme vital to anthocyanin biosynthesis.)
Ok, sorry that was a mouthful. What I really want to ask you is why the paramutation effect is not visible in the endosperm of the F1 plants? The paramutation phenotypes are presented in the F1 progeny of the plants that show anthocyanin inhibition in husk and anther tissues. Is this something to do with the endosperm development? Is the endosperm pigmentation determined by the "female" plant? I have a few ideas, but plants are not my specialty. Thank you for your time!