Table 1.
Agronomic traits of the wild-type and fon7 mutant.
Fig 1.
Grain and floral organ phenotypes of the wild-type and fon7 mutant.
(a) Occurrence of multiple grains (red arrows) in the fon7 mutant. (b, c) Wild-type (b) and fon7 mutant (c) grains. (d, e) Wild-type (d) and fon7 mutant (e) grains with hull removed. (f, g) Wild-type (f) and fon7 mutant (g) spikelets. (h) Wild-type spikelet with lemma and palea removed. Six stamens and two stigmas are visible. (i) Wild-type pistil with two stigmas. (j) fon7 spikelet with lemma and palea removed, showing seven stamens and three stigmas. (k) fon7 pistil with three stigmas. (l) fon7 spikelet with lemma and palea removed, showing six stamens and four stigmas. (m) fon7 pistil containing four stigmas, with two ovaries attached to each other. (n) fon7 spikelet with lemma and palea removed, showing eight stamens and four stigmas. (o) fon7 pistil containing four stigmas, with two ovaries separated from each other. All spikelets in five panicles of five randomly selected plants of each genotype were examined, and representative images are shown. an, anther; pi, pistil; sti, stigma.
Fig 2.
Microscopic analyses of paraffin sections of wild-type and fon7 mutant spikelets located at the basal position of the corresponding spikelets.
(a) Transverse section of wild-type spikelet. (b–d) Transverse sections of fon7 spikelets formed from flowers with three stigmas and one ovary (b), four stigmas and two fused ovaries (c), and four stigmas and two separated ovaries (d). (e–h) Transverse sections of the ovary in upper spikelets. (i–l) Sketches depicting the upper photos of paraffin sections. ca, carpel; le, lemma; lo, lodicule; ov, ovary; pa, palea; st, stamen.
Fig 3.
SNP-index graph and development of dCAPs marker.
(a) SNP-index graph generated by the MutMap analysis of the fon7 gene. Green and orange lines indicate 95% and 99% confidence intervals, respectively. Red regression lines were obtained by averaging SNP indices from a moving window of five consecutive SNPs and shifting the window one SNP at a time. Blue dots represent SNP-index values at the SNP position. Y-axis shows SNP-index values ranging from 0–1, and X-axis indicates the SNP position (Mb). Pale-yellow shaded area on chromosome 8 indicates the region corresponding to the candidate gene controlling floral organ number in rice. (b) Gene structure of Os08g0299000. Gray boxes represent exons; black lines represent introns; red star indicates the SNP position. (c) Sequence comparison between the wild-type and fon7 mutant. Red color indicates the SNP (G→A). (d) Development of the dCAPS marker for fon7. The sequence within the gray box indicates the mismatched base, which was used for developing the dCAPS marker. (e) Co-segregation of the SNP with the floral organ number phenotype of F2 plants derived from the fon7 mutant × wild-type (Ilpum) cross. PCR products were digested with MspI, and then separated on agarose gel. WT, wild-type; MT, mutant; WD, wild-type DNA fragment digested with MspI; MD, mutant DNA fragment digested with MspI.
Fig 4.
(a) cDNA sequence analysis of the fon7 locus in the mutant. (b) Gel electrophoresis of RT-PCR products of the FON7 gene in the wild-type and fon 7 mutant. (c) Gene structure of Os08g0299000 in the wild-type and mutant. Blue boxes represent exons, and gray lines represent introns. The mutation occurred in intron 6, changing G to A (splice donor variant), which caused the deletion of exon 6 (exon skipping). (d) Relative expression level of Os08g0299000 in the wild-type (WT; Ilpum) and fon7 mutant as examined by real-time quantitative PCR (qRT-PCR). Asterisks indicate significant differences (**P < 0.01; unpaired t-test). ns, non-significant.
Fig 5.
Morphological and FON7 expression phenotypes of the T-DNA-tagged line.
(a) T-DNA insertion position in the FON7 gene model. (b) Comparison of plant morphology between the wild-type and T-DNA-tagged line. (c) Wild-type spikelet. (d) Wild-type spikelet with lemma and palea removed, showing six stamens and two stigmas. (e) Spikelet of the T-DNA plant. (f, g) Spikelet of the T-DNA plant with lemma and palea removed, showing seven stamens and two stigmas (f) or eight stamens and four stigmas (g). (h) Occurrence of multiple grains in the T-DNA plant. WT, wild-type (Dongjin); T-DNA plant, PFG_3C-00521. Red arrowheads indicate seeds containing multiple grains. (i) Relative expression level of Os08g0299000 in the T-DNA plants and its corresponding wild-type (Dongjin), as examined by qRT-PCR. Asterisks indicate significant differences (**P < 0.01; unpaired t-test). ns, non-significant.
Fig 6.
Multiple sequence alignment of MEMO1 homologs.
Amino acid sequence alignment of MEMO1. Pale-blue box represents identical or similar amino acids. Zm00001d011850, Zea mays; AT2G25280, Arabidopsis thaliana; Solyc08g029110.3, Solanum lycopersicum; LOC107809489, Nicotiana tabacum; TraesCS7D02G522800, Triticum aestivum.