[1] WILLIAMS E G, MAHESWARAN G. Somatic embryogenesis: factors influencing coordinated behaviour of cells as an embryogenic group [J]. Ann Bot, 1986, 57(4): 443 − 462.
[2] HORSTMAN A, BEMER M, BOUTILIER K. A transcriptional view on somatic embryogenesis [J]. Regeneration, 2017, 4: 201 − 216.
[3] MENDEZ-HERNANDEZ H A, LEDEZMA-RODRIGUEZ M, AVILEZ-MONTALVO R N, et al. Signaling overview of plant somatic embryogenesis[J/OL]. Front Plant Sci, 2019, 10: 77[2021-01-05]. doi: 10.3389/fpls.2019.00077.
[4] JI Lexiang, MATHIONI S M, JOHNSON S, et al. Genome-wide reinforcement of DNA methylation occurs during somatic embryogenesis in soybean [J]. Plant Cell, 2019, 31(10): 2315 − 2331.
[5] WÓJCIKOWSKA B, BOTOR M, MOROŃCZYK J, et al. Trichostatin a triggers an embryogenic transition in Arabidopsis explants via an auxin-related pathway[J/OL]. Front Plant Sci, 2018, 9: 1353[2021-01-08]. doi: 10.3389/fpls.2018.01353.
[6] JIANG Fengying, RYABOVA D, DIEDHIOU J, et al. Trichostatin A increases embryo and green plant regeneration in wheat [J]. Plant Cell Rep, 2017, 36(11): 1701 − 1706.
[7] JONES T, LOWE K, HOERSTER G, et al. Maize transformation using the morphogenic genes Baby Boom and Wuschel2 [J]. Methods Mol Biol, 2019, 1864: 81 − 93.
[8] JHA P, KUMAR V. BABY BOOM (BBM): a candidate transcription factor gene in plant biotechnology [J]. Biotechnol Lett, 2018, 40(11/12): 1467 − 1475.
[9] GUZZO F, BALDAN B, LEVI M, et al. Early cellular events during induction of carrot explants with 2,4-D [J]. Protoplasma, 1995, 185(1/2): 28 − 36.
[10] RAGHAVAN V. Role of 2,4-dichlorophenoxyacetic acid (2,4-D) in somatic embryogenesis on cultured zygotic embryos of Arabidopsis: cell expansion, cell cycling, and morphogenesis during continuous exposure of embryos to 2,4-D [J]. Am J Bot, 2004, 91(11): 1743 − 1756.
[11] HALPERIN W. Alternative morphogenetic events in cell suspensions [J]. Am J Bot, 1966, 53(5): 443 − 453.
[12] MIGUEL C, MARUM L. An epigenetic view of plant cells cultured in vitro: somaclonal variation and beyond [J]. J Exp Bot, 2011, 62(11): 3713 − 3725.
[13] RAEMAKERS C J J M, JACOBSEN E, VISSER R G F. Secondary somatic embryogenesis and applications in plant breeding [J]. Euphytica, 1995, 81(1): 93 − 107.
[14] MERKLE S A, PARROTT W A, FLINN B S. Morphogenic Aspects of Somatic Embryogenesis[M]. Dordrecht: Springer, 1995.
[15] GAJ M D. Factors influencing somatic embryogenesis induction and plant regeneration with particular reference to Arabidopsis thaliana (L.) Heynh [J]. Plant Growth Regul, 2004, 43(1): 27 − 47.
[16] SCHMIDT D E, GUZZO F, TOONEN M A, et al. A leucine-rich repeat containing receptor-like kinase marks somatic plant cells competent to form embryos [J]. Development, 1997, 124(10): 2049 − 2062.
[17] PANDEY D K, CHAUDHARY B. Role of plant somatic embryogenesis receptor kinases (SERKs) in cell-to-embryo transitional activity: key at novel assorted structural subunits [J]. Am J Plant Sci, 2014, 5(21): 3177 − 3193.
[18] HECHT V, VIELLE-CALZADA J P, HARTOG M V, et al. The Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR KINASE 1 gene is expressed in developing ovules and embryos and enhances embryogenic competence in culture [J]. Plant Physiol, 2001, 127(3): 803 − 816.
[19] ALBRECHT C, RUSSINOVA E, KEMMERLING B, et al. Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR KINASE proteins serve brassinosteroid-dependent and -independent signaling pathways [J]. Plant Physiol, 2008, 148(1): 611 − 619.
[20] BRAYBROOK S A, HARADA J J. LECs go crazy in embryo development [J]. Trends Plant Sci, 2008, 13(12): 624 − 630.
[21] MEINKE D W. A homoeotic mutant of Arabidopsis thaliana with leafy cotyledons [J]. Science, 1992, 258(5088): 1647 − 1650.
[22] MEINKE D W, FRANZMANN L H, NICKLE T C, et al. Leafy cotyledon mutants of Arabidopsis [J]. Plant Cell, 1994, 6(8): 1049 − 1064.
[23] LEE H, FISCHER R L, GOLDBERG R B, et al. Arabidopsis LEAFY COTYLEDON1 represents a functionally specialized subunit of the CCAAT binding transcription factor [J]. Proc Natl Acad Sci, 2003, 100(4): 2152 − 2156.
[24] RASHID S Z, YAMAJI N, KYO M. Shoot formation from root tip region: a developmental alteration by WUS in transgenic tobacco [J]. Plant Cell Rep, 2007, 26(9): 1449 − 1455.
[25] ROCHA D I, DORNELAS M C. Molecular overview on plant somatic embryogenesis [J/OL]. CAB Rev, 2013, 8: 022[2021-01-01]. doi: 10.1079/PAVSNNR20138022.
[26] LEDWON A, GAJ M D. LEAFY COTYLEDON2 gene expression and auxin treatment in relation to embryogenic capacity of Arabidopsis somatic cells [J]. Plant Cell Rep, 2009, 28(11): 1677 − 1688.
[27] HARADA J J. Role of Arabidopsis LEAFY COTYLEDON genes in seed development [J]. J Plant Physiol, 2001, 158(4): 405 − 409.
[28] LEDWON A, GAJ M D. LEAFY COTYLEDON1, FUSCA3 expression and auxin treatment in relation to somatic embryogenesis induction in Arabidopsis [J]. Plant Growth Regul, 2011, 65(1): 157 − 167.
[29] STONE S L, KWONG L W, YEE K M, et al. LEAFY COTYLEDON2 encodes a B3 domain transcription factor that induces embryo development [J]. Proc Natl Acad Sci, 2001, 98(20): 11806 − 11811.
[30] GAZZARRINI S, TSUCHIYA Y, LUMBA S, et al. The transcription factor FUSCA3 controls developmental timing in Arabidopsis through the hormones gibberellin and abscisic acid [J]. Dev Cell, 2004, 7(3): 373 − 385.
[31] BOUTILIER K, OFFRINGA R, SHARMA V K, et al. Ectopic expression of BABY BOOM triggers a conversion from vegetative to embryonic growth [J]. Plant Cell, 2002, 14(8): 1737 − 1749.
[32] DENG Wei, LUO Keming, LI Zhengguo, et al. A novel method for induction of plant regeneration via somatic embryogenesis [J]. Plant Sci, 2009, 177(1): 43 − 48.
[33] IRIKOVA T, GROZEVA S, DENEV I. Identification of BABY BOOM and LEAFY COTYLEDON genes in sweet pepper (Capsicum annuum L.) genome by their partial gene sequences [J]. Plant Growth Regul, 2012, 67(2): 191 − 198.
[34] FLOREZ S L, ERWIN R L, MAXIMOVA S N, et al. Enhanced somatic embryogenesis in Theobroma cacao using the homologous BABY BOOM transcription factor[J/OL]. BMC Plant Biol, 2015, 15(1): 121[2020-11-08]. doi: 10.1186/s12870-015-0479-4.
[35] HEIDMANN I, de LANGE B, LAMBALK J, et al. Efficient sweet pepper transformation mediated by the BABY BOOM transcription factor [J]. Plant Cell Rep, 2011, 30(6): 1107 − 1115.
[36] JHA P, OCHATT S J, KUMAR V. WUSCHEL: a master regulator in plant growth signaling [J]. Plant Cell Rep, 2020, 39(4): 431 − 444.
[37] YADAV R K, PERALES M, GRUEL J, et al. WUSCHEL protein movement mediates stem cell homeostasis in the Arabidopsis shoot apex [J]. Genes Dev, 2011, 25(19): 2025 − 2030.
[38] SOMSSICH M, JE B I, SIMON R, et al. CLAVATA-WUSCHEL signaling in the shoot meristem [J]. Development, 2016, 143(18): 3238 − 3248.
[39] ZHANG Tianqi, LIAN Heng, ZHOU Chuanmiao, et al. A two-step model for de novo activation of WUSCHEL during plant shoot regeneration [J]. Plant Cell, 2017, 29(5): 1073 − 1087.
[40] XIAO Yanqing, CHEN Yanli, DING Yanpeng, et al. Effects of GhWUS from upland cotton (Gossypium hirsutum L.) on somatic embryogenesis and shoot regeneration [J]. Plant Sci, 2018, 270: 157 − 165.
[41] ZUO Jianru, NIU Qiwen, FRUGIS G, et al. The WUSCHEL gene promotes vegetative-to-embryonic transition in Arabidopsis [J]. Plant J, 2002, 30(3): 349 − 359.
[42] ARROYO-HERRERA A, GONZALEZ A K, MOO R C, et al. Expression of WUSCHEL in Coffea canephora causes ectopic morphogenesis and increases somatic embryogenesis [J]. Plant Cell Tissue Organ Cult, 2008, 94(2): 171 − 180.
[43] CHEN S K, KURDYUKOV S, KERESZT A, et al. The association of homeobox gene expression with stem cell formation and morphogenesis in cultured Medicago truncatula [J]. Planta, 2009, 230(4): 827 − 840.
[44] SANTA-CATARINA C, OLIVEIRA R R, CUTRI L, et al. WUSCHEL-related genes are expressed during somatic embryogenesis of the basal angiosperm Ocotea catharinensis Mez. (Lauraceae) [J]. Trees, 2012, 26(2): 493 − 501.
[45] ZHENG Wu, ZHANG Xueyan, YANG Zuoren, et al. AtWuschel promotes formation of the embryogenic callus in Gossypium hirsutum[J/OL]. PLoS One, 2014, 9(1): e87502[2020-12-11]. doi: 10.1371/journal.pone.0087502.
[46] CHATFIELD S P, CAPRON R, SEVERINO A, et al. Incipient stem cell niche conversion in tissue culture: using a systems approach to probe early events in WUSCHEL-dependent conversion of lateral root primordia into shoot meristems [J]. Plant J, 2013, 73(5): 798 − 813.
[47] BRAYBROOK S A, STONE S L, PARK S, et al. Genes directly regulated by LEAFY COTYLEDON2 provide insight into the control of embryo maturation and somatic embryogenesis [J]. Proc Natl Acad Sci, 2006, 103(9): 3468 − 3473.
[48] WOJCIKOWSKA B, JASKOLA K, GASIOREK P, et al. LEAFY COTYLEDON2 (LEC2) promotes embryogenic induction in somatic tissues of Arabidopsis, via YUCCA-mediated auxin biosynthesis [J]. Planta, 2013, 238(3): 425 − 440.
[49] HARDING E W, TANG W, NICHOLS K W, et al. Expression and maintenance of embryogenic potential is enhanced through constitutive expression of AGAMOUS-Like 15 [J]. Plant Physiol, 2003, 133(2): 653 − 663.
[50] ZHENG Yumei, REN Na, WANG Huai, et al. Global identification of targets of the Arabidopsis MADS domain protein AGAMOUS-Like15 [J]. Plant Cell, 2009, 21(9): 2563 − 2577.
[51] IKEUCHI M, SUGIMOTO K, IWASE A. Plant callus: mechanisms of induction and repression [J]. Plant Cell, 2013, 25(9): 3159 − 3173.
[52] IWASE A, MITSUDA N, KOYAMA T, et al. The AP2/ERF transcription factor WIND1 controls cell dedifferentiation in Arabidopsis [J]. Curr Biol, 2011, 21(6): 508 − 514.
[53] LEIBFRIED A, TO J P C, BUSCH W, et al. WUSCHEL controls meristem function by direct regulation of cytokinin-inducible response regulators [J]. Nature, 2005, 438(7071): 1172 − 1175.
[54] IWASE A, MITA K, NONAKA S, et al. WIND1-based acquisition of regeneration competency in Arabidopsis and rapeseed [J]. J Plant Res, 2015, 128(3): 389 − 397.
[55] WÓJCIKOWSKA B, WÓJCIK A M, GAJ M D. Epigenetic regulation of auxin-induced somatic embryogenesis in plants[J/OL]. Int J Mol Sci, 2020, 21(7): 2307[2020-12-11]. doi: 10.3390/ijms21072307.
[56] KUMAR V, van STADEN J. New insights into plant somatic embryogenesis: an epigenetic view [J]. Acta Physiol Plant, 2017, 39(9): 194.
[57] 鲁亚萍, 周明兵. 转座子沉默与DNA甲基化[J]. 浙江农林大学学报, 2021, 38(3): 634 − 643.

LU Yaping, ZHOU Mingbing. On transposon silencing and DNA methylation [J]. J Zhejiang A&F Univ, 2021, 38(3): 634 − 643.
[58]

CHAKRABARTY D, YU K W, PAEK K Y. Detection of DNA methylation changes during somatic embryogenesis of Siberian ginseng (Eleuterococcus senticosus) [J]. Plant Sci, 2003, 165(1): 61 − 68.
[59]

NOCEDA C, SALAJ T, PÉREZ M, et al. DNA demethylation and decrease on free polyamines is associated with the embryogenic capacity of Pinus nigra Arn. cell culture[J/OL]. Trees, 2009, 23(6): 1285[2021-01-01]. doi: 10.1007/s00468-009-0370-8.
[60]

BRAVO S, BERTÍN A, TURNER A, et al. Differences in DNA methylation, DNA structure and embryogenesis-related gene expression between embryogenic and non embryogenic lines of Pinus radiata D. don [J]. Plant Cell Tissue Organ Cult, 2017, 130(3): 521 − 529.
[61]

CORREDOIRA E, CANO V, BARANY I, et al. Initiation of leaf somatic embryogenesis involves high pectin esterification, auxin accumulation and DNA demethylation in Quercus alba [J]. J Plant Physiol, 2017, 213: 42 − 54.
[62]

NIC-CAN G I, LOPEZ-TORRES A, BARREDO-POOL F, et al. New insights into somatic embryogenesis: leafy cotyledon1, baby boom1 and WUSCHEL-related homeobox4 are epigenetically regulated in Coffea canephora[J/OL]. PLoS One, 2013, 8(8): e72160[2020-12-18]. doi: 10.1371/journal.pone.0072160.
[63]

GRZYBKOWSKA D, MOROŃCZYK J, WÓJCIKOWSKA B, et al. Azacitidine (5-AzaC)-treatment and mutations in DNA methylase genes affect embryogenic response and expression of the genes that are involved in somatic embryogenesis in Arabidopsis [J]. Plant Growth Regul, 2018, 85(2): 243 − 256.
[64]

YAKOVLEV I A, CARNEROS E, LEE Y, et al. Transcriptional profiling of epigenetic regulators in somatic embryos during temperature induced formation of an epigenetic memory in Norway spruce [J]. Planta, 2016, 243(5): 1237 − 1249.
[65]

SHIBUKAWA T, YAZAWA K, KIKUCHI A, et al. Possible involvement of DNA methylation on expression regulation of carrot LEC1 gene in its 5'-upstream region [J]. Gene, 2009, 437(1/2): 22 − 31.
[66]

YAMAMOTO N, KOBAYASHI H, TOGASHI T, et al. Formation of embryogenic cell clumps from carrot epidermal cells is suppressed by 5-azacytidine, a DNA methylation inhibitor [J]. J Plant Physiol, 2005, 162(1): 47 − 54.
[67]

MARGUERON R, REINBERG D. The Polycomb complex PRC2 and its mark in life [J]. Nature, 2011, 469(7330): 343 − 349.
[68]

CHANVIVATTANA Y, BISHOPP A, SCHUBERT D, et al. Interaction of Polycomb-group proteins controlling flowering in Arabidopsis [J]. Development, 2004, 131(21): 5263 − 5276.
[69]

LIU Jun, DENG Shulin, WANG Huan, et al. CURLY LEAF regulates gene sets coordinating seed size and lipid biosynthesis [J]. Plant Physiol, 2016, 171(1): 424 − 436.
[70]

IKEUCHI M, IWASE A, RYMEN B, et al. PRC2 represses dedifferentiation of mature somatic cells in Arabidopsis[J/OL]. Nat Plants, 2015, 1: 15089[2021-01-02]. doi: 10.1038/nplants.2015.89.
[71]

TANAKA M, KIKUCHI A, KAMADA H. The Arabidopsis histone deacetylases HDA6 and HDA19 contribute to the repression of embryonic properties after germination [J]. Plant Physiol, 2008, 146(1): 149 − 161.
[72]

ZHOU Yi, TAN Bin, LUO Ming, et al. HISTONE DEACETYLASE19 interacts with HSL1 and participates in the repression of seed maturation genes in Arabidopsis seedlings [J]. Plant Cell, 2013, 25(1): 134 − 148.
[73]

CHHUN T, CHONG S Y, PARK B S, et al. HSI2 repressor recruits MED13 and HDA6 to down-regulate seed maturation gene expression directly during Arabidopsis early seedling growth [J]. Plant Cell Physiol, 2016, 57(8): 1689 − 1706.
[74]

UDDENBERG D, VALLADARES S, ABRAHAMSSON M, et al. Embryogenic potential and expression of embryogenesis-related genes in conifers are affected by treatment with a histone deacetylase inhibitor [J]. Planta, 2011, 234(3): 527 − 539.
[75]

BIE Xiaomin, DONG Luhao, LI Xiaohui, et al. Trichostatin A and sodium butyrate promotes plant regeneration in common wheat[J/OL]. Plant Signal Behav, 2020, 15(12): 1820681[2020-12-20]. doi: 10.1080/15592324.2020.1820681.
[76]

IKEUCHI M, OGAWA Y, IWASE A, et al. Plant regeneration: cellular origins and molecular mechanisms [J]. Development, 2016, 143(9): 1442 − 1451.
[77]

DE-LA-PENA C, NIC-CAN G I, GALAZ-AVALOS R M, et al. The role of chromatin modifications in somatic embryogenesis in plants[J/OL]. Front Plant Sci, 2015, 6: 635[2021-01-11]. doi: 10.3389/fpls.2015.00635.
[78]

LEE K, PARK O S, JUNG S J, et al. Histone deacetylation-mediated cellular dedifferentiation in Arabidopsis [J]. J Plant Physiol, 2016, 191: 95 − 100.
[79]

GORDON-KAMM B, SARDESAI N, ARLING M, et al. Using morphogenic genes to improve recovery and regeneration of transgenic plants[J/OL]. Plants, 2019, 8(2): 38[2021-01-12]. doi: 10.3390/plants8020038.
[80]

LOWE K, WU E, WANG Ning, et al. Morphogenic regulators Baby boom and Wuschel improve monocot transformation [J]. Plant Cell, 2016, 28(9): 1998 − 2015.
[81]

MAHER M F, NASTI R A, VOLLBRECHT M, et al. Plant gene editing through de novo induction of meristems [J]. Nat Biotechnol, 2020, 38(1): 84 − 89.