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Figure 1.
Seed development in Arabidopsis and maize. (a) Schematic representation of seed development in Arabidopsis. Stages of embryo development are indicated. After fertilization, the endosperm nucleus undergoes rapid division without formation of cell walls or cytokinesis, resulting in a syncytium. Cellularization is initiated in the micropylar endosperm at the early heart embryo stage and is completed when the embryo reaches the torpedo stage. The cellularized endosperm undergoes a small series of cell proliferation until the central cell cavity is completely filled with cells. Then, the endosperm begins to breakdown, and the seed cavity is replaced by the embryo. (b) Schematic representation of seed development in B73 maize. Stages indicate days after pollination (DAP). After the syncytial endosperm proliferation and cellularization, the cellularized endosperm undergoes endoreduplication (starting at 8–10 DAP), followed by PCD (starting at about 16 DAP). The endosperm occupies the largest part of the mature kernel.
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Figure 2.
Regulation of seed size by early endosperm development. Proliferation of the syncytial endosperm nuclei and the endosperm cells during early endosperm development determines the number of endosperm cells, which plays a fundamental role in the control of seed size. The red lines represent protein-protein interactions. The blue lines represent post-transcriptional regulation. The dashed lines represent unconfirmed relationships in the endosperm or in the Arabidopsis endosperm (relationships between 'AGL62', 'ATHBs', and 'YUCs or TAAs'). Abbreviations: ABA, abscisic acid; BR, brassinolide; CK, cytokinin; GA, gibberellin; PRC2, polycomb repressive complex 2.
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Species Gene name Accession number Gene product Reference(s) Arabidopsis ABA2 AT1G52340 Short-chain dehydrogenase/reductase; involved in ABA biosynthesis [35] Arabidopsis ABI5 AT2G36270 bZIP transcription factor [34, 35] Arabidopsis AGL62 AT5G60440 MADS-box transcription factor [22, 23, 33,
40, 43, 44]Strawberry FveAGL62 FvH4_2g03030 MADS-box transcription factor [44] FveAGL80 FvH4_6g08460 Arabidopsis AHK2 AT5G35750 Histidine kinase; cytokinin receptor [62] AHK3 AT1G27320 AHK4 AT2G01830 Arabidopsis AHP2 AT3G29350 Histidine phosphotransfer protein; regulator of cytokinin signaling [63] AHP3 AT5G39340 AHP5 AT1G03430 Arabidopsis AIF2 AT3G06590 Non-DNA-binding bHLH transcription factor [70] Arabidopsis ARR1 AT3G16857 Transcription factor; involved in cytokinin signaling [64] ARR10 AT4G31920 ARR12 AT2G25180 Strawberry FveATHB29b FvH4_5g17830 ATHB subfamily of transcription factor [44] FveATHB30 FvH4_6g48610 Arabidopsis AXL AT2G32410 Subunit of the RUB1 activating enzyme; involved in auxin signaling [38, 39] AXR1 AT1G05180 Arabidopsis BBM AT5G17430 AP2/ERF transcription factor [25] Arabidopsis BPC1 AT2G01930 BPC transcription factor [100] BPC2 AT1G14685 Arabidopsis BZR1 AT1G75080 Transcription factor; involved in BR signaling [69] Arabidopsis CKI1 AT2G47430 Histidine kinase without cytokinin perception domain; involved in cytokinin signaling [61] Arabidopsis CKX2 AT2G19500 Cytokinin oxidase; involved in cytokinin homeostasis [27] Rice OsEMF2a Os04g08034 Polycomb group protein [53, 95] Arabidopsis FIE AT3G20740 Polycomb group protein [22, 24] Rice OsFIE1 Os08g04290 Polycomb group protein [94] Rice OsFIE2 Os08g04270 Polycomb group protein [90, 91, 93] Arabidopsis FIS2 AT2G35670 Polycomb group protein [24, 40, 43] Arabidopsis FUS3 AT3G26790 B3 domain transcription factor [100] Arabidopsis IKU1 AT2G35230 VQ motif protein [17−19, 27] Arabidopsis IKU2 AT3G19700 LRR-RLK [17, 19−21, 26, 27] Maize ZmIPT2 Zm00001d003869 Isopentenyl transferase; involved in cytokinin biosynthesis [57, 60] Arabidopsis MEA AT1G02580 Polycomb group protein [24, 43] Soybean GmMEA Gm11G067000 Polycomb group protein [26] Arabidopsis MINI3 AT1G55600 WRKY transcription factor [18−21, 27] Arabidopsis MIR159A AT1G73687 microRNA159 [31] MIR159B AT1G18075 MIR159C AT2G46255 Maize Zma-miR169o MI0013202 microRNA169o [15] Arabidopsis MSI1 AT5G58230 Polycomb group protein [24] Rice MISSEN XLOC_057324 Long noncoding RNA [32] Arabidopsis MYB33 AT5G06100 MYB transcription factor [31] MYB65 AT3G11440 Arabidopsis NAA10 AT5G13780 Catalytic subunit of Arabidopsis NatA complex [33] Arabidopsis NAA15 AT1G80410 Auxiliary subunit of Arabidopsis NatA complex [33] Maize ZmNF-YA13 Zm00001d018255 Nuclear factor Y, subunit A [15] Rice OsNF-YB1 Os02g49410 Nuclear factor Y, subunit B [46] Arabidopsis PHE1 AT1G65330 MADS-box transcription factor [96−99] Arabidopsis PLT2 AT1G51190 AP2/EREBP transcription factor [25] Arabidopsis RAN1 AT5G20010 Ras-related nuclear GTPase [34] RAN2 AT5G20020 RAN3 AT5G55190 Arabidopsis RAV1 AT1G13260 AP2/B3 domain transcription factor [76] Arabidopsis SHB1 AT4G25350 SYG1 family protein; transcription coactivator [20−22, 35] Arabidopsis TAR1 AT1G23320 Tryptophan aminotransferase; involved in auxin biosynthesis [38, 39] TAR2 AT4G24670 Arabidopsis TFL1 AT5G03840 Phosphatidylethanolamine binding protein [34] Arabidopsis WEI8 AT1G70560 Tryptophan aminotransferase; involved in auxin biosynthesis [38, 39] Maize ZmYUC1 Zm00001d023718 Flavin monooxygenase; involved in auxin biosynthesis [15, 47] Rice OsYUC11 Os12g08780 Flavin monooxygenase; involved in auxin biosynthesis [46] Table 1.
Genes involved in seed size control by early endosperm development.
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