Fig. 1: A cytological analysis of chromosome behaviour and CO counts in scep3.
From: SCEP3 initiates synapsis and implements crossover interference in Arabidopsis
a–t, Representative DAPI-stained meiotic chromosomes from a sample of 50 wild-type (a–j) and scep3-2 (k–t) cells. Leptotene (a,k), zygotene (b,l), pachytene (c,m) (the insets show gaps between homologous chromosomes), diplotene (d,n), diakinesis (e,o) (in o and p, white circles mark a pair of univalents), metaphase I (f,p), anaphase I (g,q), telophase I (h,r), anaphase II (i,s) and the tetrad stage (j,t) are shown. u–y, DAPI-stained meiotic metaphase I chromosomes labelled with 5S and 45S rDNA and chiasma counts from individual chromosomes. The images show the wild type (u), scep3-2+/− (v) and scep3-2−/− (w), with chromosome numbers in white. Panel x shows chiasma counts per cell (the data are presented as mean ± s.d., and the asterisks indicate significant differences (***P < 0.0001, two-tailed Mann–Whitney U-test)) for the wild type (WT) (n = 58 cells), scep3-2+/− (n = 58 cells) and scep3-2−/− (n = 52 cells). Panel y shows chiasma counts per chromosome. z–c′, At late meiotic prophase I, HEI10 foci mark class I CO sites in the wild type and scep3-2. Co-immunofluorescence of SMC3 (magenta) with HEI10 (cyan) in the wild type (z), scep3-2+/− (a′) (the white circles highlight clusters of HEI10) and scep3-2−/− (b′). Panel c′ shows the HEI10 foci counts per cell (the data are presented as mean ± s.d.) in the wild type (n = 21 cells), scep3-2+/− (n = 30 cells) and scep3-2−/− (n = 30 cells). The asterisks indicate significant differences (***P < 0.0001, two-tailed Mann–Whitney U-test). d′, Chromosome configurations at meiotic metaphase I presented relative to the five chromosome pairs of A. thaliana. e′, qPCR shows reduced expression of full-length and truncated SCEP3 transcripts in scep3-2 mutants. Expression of SCEP3 was normalized against ACTIN and is shown relative to the mean expression in the wild type. The data are represented as mean ± s.e.m. (n = 3 biological replicates, each consisting of a pool of 10 plants). Statistical significance was determined using two-tailed Welch’s t-tests. The asterisks indicate significant differences (for full-length SCEP3, P = 0.003 for scep3-2−/− and P = 0.002 for scep3-2+/−); for truncated SCEP3, P = 0.006 for scep3-2−/−). Scale bars, 10 µm.
