Expression patterns of class I KNOX and YABBY genes in Ruscus aculeatus (Asparagaceae) with implications for phylloclade homology

Hirayama, Yumiko; Yamada, Toshihiro; Oya, Yoko; Itô, Motomi; Kato, Masahiro; Imaichi, Ryoko

doi:10.1007/s00427-007-0149-0

Cited by 25 publications

(20 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Two recently published papers regarding monocot STM genes (40,41) and also our unpublished analysis strongly suggest that the STM ortholog was lost in the Poaceae. The Poaceae kn1 gene is related to KNAT1.…”

supporting

confidence: 55%

Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

Uchida

Townsley

Chung

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The indeterminate shoot apical meristem of plants is characterized by the expression of the Class 1 KNOTTED1-LIKE HOMEOBOX (KNOX1) genes. KNOX1 genes have been implicated in the acquisition and/or maintenance of meristematic fate. One of the earliest indicators of a switch in fate from indeterminate meristem to determinate leaf primordium is the down-regulation of KNOX1 genes orthologous to SHOOT MERISTEMLESS (STM) in Arabidopsis (hereafter called STM genes) in the initiating primordia. In simple leafed plants, this down-regulation persists during leaf formation. In compound leafed plants, however, KNOX1 gene expression is reestablished later in the developing primordia, creating an indeterminate environment for leaflet formation. Despite this knowledge, most aspects of how STM gene expression is regulated remain largely unknown. Here, we identify two evolutionarily conserved noncoding sequences within the 5 upstream region of STM genes in both simple and compound leafed species across monocots and dicots. We show that one of these elements is involved in the regulation of the persistent repression and/or the reestablishment of STM expression in the developing leaves but is not involved in the initial down-regulation in the initiating primordia. We also show evidence that this regulation is developmentally significant for leaf formation in the pathway involving ASYMMETRIC LEAVES1/2 (AS1/2) gene expression; these genes are known to function in leaf development. Together, these findings reveal a regulatory point of leaf development mediated through a conserved, noncoding sequence in STM genes.evolution ͉ KNOX1 ͉ shoot apical meristem T he shoot apical meristem (SAM) of plants is an indeterminate structure and the source of stem cells from which all aerial organs are derived. Indeterminacy during development is regulated by a suite of genes that function in the SAM. The process of organ initiation begins when cells in the incipient organ primordium change identity from indeterminate to determinate. The indeterminate SAM is characterized by the expression of the Class 1 KNOTTED1-LIKE HOMEOBOX (KNOX1) genes. KNOX1 genes have been implicated in the acquisition and/or maintenance of meristematic fate (1, 2). One of the earliest indicators of a switch in fate from indeterminate meristem to determinate leaf primordium is the down-regulation of KNOX1 genes orthologous to SHOOT MERISTEMLESS (STM) in Arabidopsis (hereafter called STM genes) in the incipient primordia (1).The SAM can give rise to two different leaf forms, simple or compound (3), and KNOX1 genes are down-regulated in the incipient primordia in both compound and simple leafed species. In simple leafed plants, this down-regulation persists during leaf formation (4-7), and overexpression of these genes is sufficient to cause leaf lobing and ectopic meristem formation (8-11). However, KNOX1 expression is reestablished later in the developing primordia of compound leafed plants (12-15). Additionally, overexpression of KNOX1 genes in transgenic tomato plants or spo...

show abstract

supporting

confidence: 55%

Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

Uchida

Townsley

Chung

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…The monocot Ruscus (Asparagaceae) has leaf-like, determinate stems (phylloclades) in the axil of scaly leaves (Arber, 1924). Molecular genetic studies in these two cases have suggested that the key regulatory genes for both SAM and leaf development are expressed in the same organ (Harrison et al, 2005;Hirayama et al, 2007), implying that similar network cooption of genes may be involved in the evolution of those shootleaf mixed organs.…”

Section: Evolution Of Novel Shoot Organogenesis Of Podostemoideaementioning

confidence: 99%

Expression ofSHOOT MERISTEMLESS,WUSCHEL, andASYMMETRIC LEAVES1Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis

2010

Self Cite

View full text Add to dashboard Cite

Podostemaceae (the river weeds) are ecologically and morphologically unusual angiosperms. The subfamily Tristichoideae has typical shoot apical meristems (SAMs) that produce leaves, but Podostemoideae is devoid of SAMs and new leaves arise below the base of older leaves. To reveal the genetic basis for the evolution of novel shoot organogenesis in Podostemaceae, we examined the expression patterns of key regulatory genes for shoot development (i.e., SHOOT MERISTEMLESS (STM), WUSCHEL (WUS), and ASYMMETRIC LEAVES1/ROUGH SHEATH2/PHANTASTICA (ARP) orthologs) in Tristichoideae and Podostemoideae. In the SAM-mediated shoots of Tristichoideae, like in model plants, STM and WUS orthologs were expressed in the SAM. In the SAM-less shoots of Podostemoideae, STM and WUS orthologs were expressed in the initiating leaf/bract primordium. In older leaf/bract primordia, WUS expression disappeared and STM expression became restricted to the basal part, whereas ARP was expressed in the distal part in a complementary pattern to STM expression. In the reproductive shoots of Podostemoideae with a normal mode of flower development, STM and WUS were expressed in the floral meristem, but not in the floral organs, similar to the pattern in model plants. These results suggest that the leaf/bract of Podostemoideae is initiated as a SAM and differentiates into a single apical leaf/bract, resulting in the evolution of novel shoot-leaf mixed organs in Podostemaceae.

show abstract

“…Phylloclades differ from cladodes in consisting of a stem with multiple internodes (Bell, 2008). Expression analysis by PCR showed that the STM and YABBY orthologs are expressed in phylloclades (Hirayama et al, 2007). However, both anatomical (Conran and Tamura, 1998;Rudall et al, 1998) and molecular phylogenetic analyses (Kim et al, 2010) suggest that the evolution of leaf-like axillary shoots occurred independently in Asparagus and Ruscus.…”

Section: Acquisition Of Leaf-like Organs In Asparagaceae and The Divementioning

confidence: 99%

“…Cladodes have so far been considered to be either modified stems, ectopic leaves, or de novo organs (Hirsch, 1977;CooneySovetts and Sattler, 1986;Hirayama et al, 2007). Under any of these interpretations, clarifying the genetic regulation of cladode development could help answer some outstanding questions.…”

Section: Introductionmentioning

confidence: 99%

Acquisition and Diversification of Cladodes: Leaf-Like Organs in the Genus Asparagus

2012

View full text Add to dashboard Cite

The genus Asparagus is unusual in producing axillary, determinate organs called cladodes, which may take on either a flattened or cylindrical form. Here, we investigated the evolution of cladodes to elucidate the mechanisms at play in the diversification of shoot morphology. Our observations of Asparagus asparagoides, which has leaf-like cladodes, showed that its cladodes are anatomically and developmentally similar to leaves but differ in the adaxial/abaxial polarity of the vasculature. In addition to the expression of an ortholog of KNAT1, orthologous genes that are normally expressed in leaves, ASYMMETRIC LEAVES1 and HD-ZIPIII, were found to be expressed in cladode primordia in a leaf-like manner. The cylindrical cladodes of Asparagus officinalis showed largely similar expression patterns but showed evidence of being genetically abaxialized. These results provide evidence that cladodes are modified axillary shoots, suggest that the cooption of preexisting gene networks involved in leaf development transferred the leaf-like form to axillary shoots, and imply that altered expression of leaf polarity genes led to the evolution of cylindrical cladodes in the A. officinalis clade.

show abstract

Expression patterns of class I KNOX and YABBY genes in Ruscus aculeatus (Asparagaceae) with implications for phylloclade homology

Cited by 25 publications

References 44 publications

Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

Regulation of SHOOT MERISTEMLESS genes via an upstream-conserved noncoding sequence coordinates leaf development

Expression ofSHOOT MERISTEMLESS,WUSCHEL, andASYMMETRIC LEAVES1Homologs in the Shoots of Podostemaceae: Implications for the Evolution of Novel Shoot Organogenesis

Acquisition and Diversification of Cladodes: Leaf-Like Organs in the Genus Asparagus

Contact Info

Product

Resources

About