Flowering genes in Metrosideros fit a broad herbaceous model encompassing Arabidopsis and Antirrhinum

Abstract

Molecular studies were conducted on Metrosideros excelsa to determine if the current genetic models for flowering with regard to inflorescence and floral meristem identity genes in annual plants were applicable to a woody perennial. MEL, MESAP1 and METFL1, the fragments of LEAFY (LFY), APETALA1 (AP1) and TERMINAL FLOWER1 (TFL1) equivalents, respectively, were isolated from M. excelsa. Temporal expression patterns showed that MEL and MESAP1 exhibited a bimodal pattern of expression. Expression exhibited during early floral initiation in autumn was followed by down-regulation during winter, and up-regulation in spring as floral organogenesis occurred. Spatial expression patterns of MEL showed that it had greater similarity to FLORICAULA (FLO) than to LFY, whereas MESAP1 was more similar to AP1 than SQUAMOSA. The interaction between MEL and METFL1 was more similar to the interaction between FLO and CENTRORADIALIS than that between LFY and TFL1. Consequently, the three genes from M. excelsa fit a broader herbaceous model encompassing Antirrhinum as well as Arabidopsis, but with differences, such as the bimodal pattern of expression seen with MEL and MESAP1. In mid-winter, at the time when both MEL and MESAP1 were down-regulated, GA(1) was below the level of detection in M. excelsa buds. Even though application of gibberellin inhibits flowering in members of the Myrtaceae, MEL was responsive to gibberellin with expression in juvenile plants up-regulated by GA(3). However, MESAP1 was not up-regulated indicating that meristem competence was also probably required to promote flowering in M. excelsa.

Effect of environment and shoot architecture on floral transition and gene expression in Eucalyptus occidentalis and Metrosideros excelsa

“…Similar bimodal expression and developmental events have been observed in Actinidia (Walton et al 2001), Vitis (Carmona et al 2002), Populus (Cseke and Podila 2004), and Metrosideros (Sreekantan et al 2004) although in these cases the dormant period occurred during winter. Expression of the StLFY in Sophora was relatively low at the time of inflorescence initiation (Song et al 2008), although Walton et al (2001) and Sreekantan et al (2004) found LFY homologues to be upregulated at this time.…”

“…Floral induction occurs in autumn (Sreekantan et al 2001) and while floral primordia are microscopically evident by May, organ differentiation does not occur until September. Sreekantan et al (2004) showed elevated MESAP1 and MEL expression in buds during cymule formation and again later during organ differentiation. Ambient (winter) conditions were shown by Henriod et al (2000Henriod et al ( , 2003 to be conducive to full floral development.…”

A Genomic and Expression Compendium of the ExpandedPEBPGene Family from Maize

“…Two distinct TFL1 homologs control pea (Pisum sativum) vegetative and reproductive phase duration: The LATE FLOWERING gene maintains shoot apical meristem indeterminacy, and DE-TERMINATE (DET) maintains inflorescence meristem indeterminacy (Foucher et al, 2003). TFL1 homologs with conserved function have now been identified in many eudicotyledonous (Amaya et al, 1999;Pillitteri et al, 2004;Sreekantan et al, 2004;Kotoda and Wada, 2005;Boss et al, 2006;Kim et al, 2006) and monocotyledonous plants (Jensen et al, 2001;Nakagawa et al, 2002;Zhang et al, 2005). The Arabidopsis TFL1 protein has recently been shown to be a mobile signal that moves from its localized transcriptional domain in the central region of the inflorescence meristem to the entire meristem, where it exerts its activity.…”

Concerted Modification of Flowering Time and Inflorescence Architecture by Ectopic Expression ofTFL1-Like Genes in Maize

“…In general, the structure and function of TFL1-related proteins are greatly conserved (Kato et al, 1998;Pnueli et al, 1998;Jensen et al, 2001;Nakagawa et al, 2002;Carmel-Goren et al, 2003;Sreekantan et al, 2004;Chardon and Damerval, 2005;Esumi et al, 2005;Kotoda and Wada, 2005;Zhang et al, 2005;Boss et al, 2006;Guo et al, 2006;Kim et al, 2006;Argiriou et al, 2008;Datta et al, 2008;Igasaki et al, 2008;Elitzur et al, 2009;Hiroyuki et al, 2009;Mimida et al, 2009). However, there is evidence for diversification and specification of the function of different TFL1 family members.…”