Limits...
Flower development of Phalaenopsis orchid involves functionally divergent SEPALLATA-like genes.

Pan ZJ, Chen YY, Du JS, Chen YY, Chung MC, Tsai WC, Wang CN, Chen HH - New Phytol. (2014)

Bottom Line: The tepal became a leaf-like organ when PeSEP3 was silenced by virus-induced silencing, with alterations in epidermis identity and contents of anthocyanin and chlorophyll.Silencing of the E-class genes PeSEP2 and PeSEP3 resulted in the downregulation of B-class PeMADS2-6 genes, which indicates an association of PeSEP functions and B-class gene expression.These findings reveal the important roles of PeSEP in Phalaenopsis floral organ formation throughout the developmental process by the formation of various multiple protein complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, National Cheng Kung University, Tainan, 701, Taiwan.

Show MeSH

Related in: MedlinePlus

Schematic representation of the proposed regulatory network of Phalaenopsis PeSEP genes in the regulation of floral development. Arrows indicate the direction of the transcriptional regulatory pathway. The broken lines show that PeSEP2 may act as an upstream regulator to initiate PeSEP expression. The combinatory network of PeSEPs may coordinately regulate downstream targets, such as MIXTA-like, PeMYBs and EREBP-like genes, to promote flower morphogenesis and to inhibit leaf-like characteristics. The graphical representation of various organs does not reflect the real growth architecture of Phalaenopsis. B-class proteins, PeMADS2–5 and PeMADS6 are referred to as AP3 and PI homologs, respectively. Abbreviations: PeM2–PeM6, PeMADS2–6.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4288972&req=5

fig12: Schematic representation of the proposed regulatory network of Phalaenopsis PeSEP genes in the regulation of floral development. Arrows indicate the direction of the transcriptional regulatory pathway. The broken lines show that PeSEP2 may act as an upstream regulator to initiate PeSEP expression. The combinatory network of PeSEPs may coordinately regulate downstream targets, such as MIXTA-like, PeMYBs and EREBP-like genes, to promote flower morphogenesis and to inhibit leaf-like characteristics. The graphical representation of various organs does not reflect the real growth architecture of Phalaenopsis. B-class proteins, PeMADS2–5 and PeMADS6 are referred to as AP3 and PI homologs, respectively. Abbreviations: PeM2–PeM6, PeMADS2–6.

Mentions: By studying loss-of-function mutants, several species of dicots have shown a general conservation of SEP-like gene functions in the specification of floral organ identity. The Arabidopsis sep1sep2sep3 triple mutants have a phenotype of all sepals, petals, stamens and carpels converted to sepal-like organs, whereas the sep1sep2sep3sep4 mutant has the most striking changes, with all floral organs replaced by leaf-like organs (Pelaz et al., 2000; Ditta et al., 2004). Downregulation of SEP1/2-like genes in tomato (LeTM29) and petunia (FBP2 and FBP5) produces sepallata-like flowers (Ampomah-Dwamena et al., 2002; Vandenbussche et al., 2003; Matsubara et al., 2008). Similar phenotypes were found when silencing ripening-related genes: FaMADS9 in strawberry and MaMADS8 and MaMADS9 in apple (Seymour et al., 2010; Ireland et al., 2013). The Petunia PhAGL6 shows similar expression patterns, but also redundant functions, to FBP2/FBP5 (Rijpkema et al., 2009). In monocots, grass species have been analyzed for loss of function of SEP-like genes in floral organ identity. Simultaneous silencing of rice OsMADS1,OsMADS5,OsMADS7 and OsMADS8 transformed all floret organs into leaf-like structures (Cui et al., 2010). Our analysis of PeSEP silencing is the first species investigated other than Poaceae. Although functions of orchid SEP-like genes have been characterized by ectopic expression in Arabidopsis in two species, Oncidium and Dendrobium (Yu & Goh, 2000; Chang et al., 2009), VIGS of PeSEP genes in Phalaenopsis allows for a much more comprehensive and detailed understanding of their functions. We found that the PeSEP-silenced perianth was unable to maintain its distinctive nature as an elaborate floral tepal, but rather converted to an organ with leaf-like appearance. Silencing of the PeSEP genes was sufficient to promote homeotic transformation with reduced flower size and delayed perianth senescence in leaf-like perianth. PeSEPs may trigger a change in the original cell identity from a leaf to perianth via broad changes in cellular levels by cell expansion, inhibition of chlorophyll accumulation, anthocyanin pigmentation, cutin formation and extracellular structures (Fig.12).


Flower development of Phalaenopsis orchid involves functionally divergent SEPALLATA-like genes.

Pan ZJ, Chen YY, Du JS, Chen YY, Chung MC, Tsai WC, Wang CN, Chen HH - New Phytol. (2014)

Schematic representation of the proposed regulatory network of Phalaenopsis PeSEP genes in the regulation of floral development. Arrows indicate the direction of the transcriptional regulatory pathway. The broken lines show that PeSEP2 may act as an upstream regulator to initiate PeSEP expression. The combinatory network of PeSEPs may coordinately regulate downstream targets, such as MIXTA-like, PeMYBs and EREBP-like genes, to promote flower morphogenesis and to inhibit leaf-like characteristics. The graphical representation of various organs does not reflect the real growth architecture of Phalaenopsis. B-class proteins, PeMADS2–5 and PeMADS6 are referred to as AP3 and PI homologs, respectively. Abbreviations: PeM2–PeM6, PeMADS2–6.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4288972&req=5

fig12: Schematic representation of the proposed regulatory network of Phalaenopsis PeSEP genes in the regulation of floral development. Arrows indicate the direction of the transcriptional regulatory pathway. The broken lines show that PeSEP2 may act as an upstream regulator to initiate PeSEP expression. The combinatory network of PeSEPs may coordinately regulate downstream targets, such as MIXTA-like, PeMYBs and EREBP-like genes, to promote flower morphogenesis and to inhibit leaf-like characteristics. The graphical representation of various organs does not reflect the real growth architecture of Phalaenopsis. B-class proteins, PeMADS2–5 and PeMADS6 are referred to as AP3 and PI homologs, respectively. Abbreviations: PeM2–PeM6, PeMADS2–6.
Mentions: By studying loss-of-function mutants, several species of dicots have shown a general conservation of SEP-like gene functions in the specification of floral organ identity. The Arabidopsis sep1sep2sep3 triple mutants have a phenotype of all sepals, petals, stamens and carpels converted to sepal-like organs, whereas the sep1sep2sep3sep4 mutant has the most striking changes, with all floral organs replaced by leaf-like organs (Pelaz et al., 2000; Ditta et al., 2004). Downregulation of SEP1/2-like genes in tomato (LeTM29) and petunia (FBP2 and FBP5) produces sepallata-like flowers (Ampomah-Dwamena et al., 2002; Vandenbussche et al., 2003; Matsubara et al., 2008). Similar phenotypes were found when silencing ripening-related genes: FaMADS9 in strawberry and MaMADS8 and MaMADS9 in apple (Seymour et al., 2010; Ireland et al., 2013). The Petunia PhAGL6 shows similar expression patterns, but also redundant functions, to FBP2/FBP5 (Rijpkema et al., 2009). In monocots, grass species have been analyzed for loss of function of SEP-like genes in floral organ identity. Simultaneous silencing of rice OsMADS1,OsMADS5,OsMADS7 and OsMADS8 transformed all floret organs into leaf-like structures (Cui et al., 2010). Our analysis of PeSEP silencing is the first species investigated other than Poaceae. Although functions of orchid SEP-like genes have been characterized by ectopic expression in Arabidopsis in two species, Oncidium and Dendrobium (Yu & Goh, 2000; Chang et al., 2009), VIGS of PeSEP genes in Phalaenopsis allows for a much more comprehensive and detailed understanding of their functions. We found that the PeSEP-silenced perianth was unable to maintain its distinctive nature as an elaborate floral tepal, but rather converted to an organ with leaf-like appearance. Silencing of the PeSEP genes was sufficient to promote homeotic transformation with reduced flower size and delayed perianth senescence in leaf-like perianth. PeSEPs may trigger a change in the original cell identity from a leaf to perianth via broad changes in cellular levels by cell expansion, inhibition of chlorophyll accumulation, anthocyanin pigmentation, cutin formation and extracellular structures (Fig.12).

Bottom Line: The tepal became a leaf-like organ when PeSEP3 was silenced by virus-induced silencing, with alterations in epidermis identity and contents of anthocyanin and chlorophyll.Silencing of the E-class genes PeSEP2 and PeSEP3 resulted in the downregulation of B-class PeMADS2-6 genes, which indicates an association of PeSEP functions and B-class gene expression.These findings reveal the important roles of PeSEP in Phalaenopsis floral organ formation throughout the developmental process by the formation of various multiple protein complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, National Cheng Kung University, Tainan, 701, Taiwan.

Show MeSH
Related in: MedlinePlus