Increased CiFT abundance in the stem correlates with floral induction by low temperature in Satsuma mandarin (Citrus unshiu Marc.)

Abstract

After several years in the juvenile phase, adult citrus trees show seasonal periodicity of flowering. A prolonged exposure to low temperature is one of the most important environmental cues for floral induction in citrus. In the present study, the expression of flowering-related genes during the annual cycle of flowering and inductive low-temperature treatment in Satsuma mandarin (Citrus unshiu Marc.) trees is investigated. Simultaneously, floral induction, which occurs before the period of morphological flower development, was estimated as the number of flowers after the forcing of sprouting by defoliation at 25 degrees C. The expression of citrus FLOWERING LOCUS T homologues, CiFT, showed a seasonal increase during the floral induction period and was also induced by an artificial low-temperature treatment (15 degrees C) at which floral induction occurred. By contrast, the mRNA level of CiFT did not show any distinct changes following a warm-temperature treatment (25 degrees C) for 2.5 months, during which time floral induction was completely suppressed. Changes in the expression of the citrus homologues of TERMINAL FLOWER 1, LEAFY, and APETALA1 did not show any correlation with floral induction in the field or under artificial low-temperature conditions. In juvenile seedlings of Satsuma mandarin, which does not flower even under inductive low-temperature conditions, the mRNA levels of CiFT were not affected by the low-temperature treatment, unlike adult tissues. These results suggest that low temperature promotes floral induction via the activation of CiFT transcription in adult Satsuma mandarin trees and that, in the juvenile plant, CiFT transcription does not respond to low temperature.

Contributions of Flowering Time Genes to Sunflower Domestication and Improvement

“…Thus, our findings challenge the prediction that downstream genes like FT are more likely to exhibit regulatory variation (Schwartz et al 2009). The redundancy afforded by a recent history of duplication, the novel derived expression domain of HaFT1, or multifarious selection acting on multiple pleiotropic effects may have uniquely fostered a selective sweep on a structural change in this case (Blackman et al 2010); however, given the expansion of FT/TFL1 homolog numbers observed in other species (Carmel-Goren et al 2003;Faure et al 2007;Nishikawa et al 2007;Danilevskaya et al 2008;Igasaki et al 2008;Mimida et al 2009), similar results may soon be observed in additional systems. FIGURE S1.-Sunflower COL homologs cluster with the CO-COL1-COL2 clade.…”

Ambiente y reguladores de crecimiento en la expresión de Flowering Locus T en mango

“…Actualmente, la identificación, cuantificación y expresión de genes relacionados con floración constituye una herramienta importante para entender el proceso desde inducción, iniciación y diferenciación floral en muchos frutales (Nishikawa et al, 2007;Muñoz et al, 2012). En mango, varios estudios mencionan que las hojas maduras son capaces de percibir el estímulo ambiental para floración y producir grandes cantidades de "florígero" bajo condiciones inductivas y transportarlo al meristemo apical desde una distancia de hasta 100 cm en condiciones subtropicales y de 52 en tropicales (Davenport y Ying, 2004;Davenport et al, 2006; Ramírez y Davenport, 2010).…”

“…Currently, identification, quantification and expression of genes related to flowering is an important tool for understanding the process from induction, floral initiation and differentiation in many fruit (Nishikawa et al, 2007;Muñoz et al, 2012) bIn mango, several studies mention that the mature leaves are able to perceive the environmental stimulus for flowering and produce large amounts of "florigero" under inductive conditions and transport it to the apical meristem from a distance of up to 100 cm in subtropical conditions and 52 in tropical (Davenport and Ying, 2004;Davenport et al, 2006;Ramírez and Davenport, 2010). The floral induction is manifested by the generation of this "flower" on the leaf, apparently unknown.…”

“…En tropicales, los estudios generalmente incluyen una relación de la expresión del gene con la iniciación y desarrollo floral, ambiente y reguladores de crecimiento. En mandarina 'Satsuma' los niveles del gene homólogo FT incrementaron con temperaturas frías durante el tiempo de inducción floral (Nishikawa et al, 2007) y en naranjo dulce hay evidencias que los niveles de homólogos leafy (LFY) y apetala (AP1) incrementan durante y después de la inducción floral con temperaturas frías (Pillitteri et al, 2004).…”

“…In tropical, studies generally include a relationship of gene expression with initiation and floral development, environment and growth regulators. In 'Satsuma' mandarin, levels of the homologous FT gene increased with cold temperatures during floral induction time (Nishikawa et al, 2007) and in sweet orange there is evidence that levels of leafy (LFY) and apetala (AP1) homologues increase during and after floral induction with cold temperatures (Pillitteri et al, 2004).…”