Constitutive expression of Arabidopsis LEAFY or APETALA1 genes in citrus reduces their generation time

Abstract

Citrus trees have a long juvenile phase that delays their reproductive development by between 6 and 20 years, depending on the species. With the aim of accelerating their flowering time, we transformed juvenile citrus seedlings to constitutively express the Arabidopsis LEAFY (LFY) or APETALA1 (AP1) genes, which promote flower initiation in Arabidopsis. Both types of transgenic citrus produced fertile flowers and fruits as early as the first year, notably through a mechanism involving an appreciable shortening of their juvenile phase. Furthermore, expression of AP1 was as efficient as LFY in the initiation of flowers, and did not produce any severe developmental abnormality. Both types of transgenic trees flowered in consecutive years, and their flowering response was under environmental control. In addition, zygotic and nucellar derived transgenic seedlings had a very short juvenile phase and flowered in their first spring, demonstrating the stability and inheritance of this trait. These results open new possibilities for domestication, genetic improvement, and experimental research in citrus and other woody species.

Ectopic expression of Atleafy in Brassica juncea cv. Geeta for early flowering

“…4). Early onset of flowering in transgenic plants is in concordance with the earlier reports of Leafy overexpression in different species tobacco Nilsson 1995), aspen (Wiegel andNilsson 1995), rice (He et al 2000), poplar (Rottmann et al 2000), citrus (Pena et al 2001) and B. juncea (Roy et al 2009). The PCR positive lines also showed different morphological defects.…”

“…Gray ex Hook.) (Rottmann et al 2000), and Citrus (Pena et al 2001). This ability of LFY to accelerate flowering is tapped in this study to develop early flowering transgenics of Brassica by overexpression of AtLFY.…”

Agrobacterium-mediated genetic transformation of 'Hamlin' sweet orange

“…So far, there are few reports of the introduction of agronomical important genes in citrus: encoding for the citrus tristeza virus coat protein (Gutiérrez et al, 1997;Domínguez et al, 2000;Yang et al, 2000), HAL2 gene, for tolerance-to-salinity (Cervera et al, 2000) and LEAFY and APETALA1 genes which promote flower initiation (Peña et al, 2001).…”

Transformação genética de laranja doce (Citrus sinensis L. Osbeck) com o gene cecropin MB39 e avaliação de plantas transgênicas inoculadas com Xylella fastidiosa Wells et al.

“…Nos trabalhos de transformação genética em citros, é bastante comum a utilização do gene de seleção nptII, que confere resistência ao antibiótico canamicina, assim como a utilização do gene repórter GUS PEÑA et al, 2001;MENDES et al, 2002;MOLINARI et al, 2004;AZEVEDO et al, 2006) ou GFP (GHORBEL et al, 1999;FLEMING et al, 2000). Entretanto, muitos trabalhos relatam um grande número de escapes (gemas adventícias regeneradas não transformadas), indicando que a canamicina restringe mas não inibe completamente a regeneração de escapes (PEÑA et al, 1997).…”