Lack of maize ATR results in enhanced cell death in endosperm. A, Progression of endosperm cell death in ATR-B WT and Zmatr-b kernels at indicated DAP, as indicated by Evans Blue staining. Dead cells are dark-stained. Scale bar = 3 mm. B, Quantification of the percentage of cell death within the endosperm area in ATR-A and ATR-B WT, and Zmatr-a and Zmatr-b mutants. All analyses were carried out from at least seven kernels of three independent cobs for each genotype. Values are means ± se; n = 21 (***P < 0.001, Student’s t-test). See also Supplemental Data Set S1. C, Expression levels of the BFN1-2 and PASPA3-2 transcripts in ATR-B WT and Zmatr-b endosperms at 16 and 19 DAP. RNA was extracted from an endosperm pool extracted from at least three kernels of three cobs for each genotype, and the expression levels were measure by quantitative RT-qPCR. Each bar shows the mean ± standard deviation (sd) sd of three biological replicates (**P < 0.05; **P < 0.01, Student’s t-test). See also Supplemental Data Set S1.