Floral Meristem Identity Genes Are Expressed during Tendril Development in Grapevine

Abstract

To study the early steps of flower initiation and development in grapevine (Vitis vinifera), we have isolated two MADS-box genes, VFUL-L and VAP1, the putative FUL-like and AP1 grapevine orthologs, and analyzed their expression patterns during vegetative and reproductive development. Both genes are expressed in lateral meristems that, in grapevine, can give rise to either inflorescences or tendrils. They are also coexpressed in inflorescence and flower meristems. During flower development, VFUL-L transcripts are restricted to the central part of young flower meristems and, later, to the prospective carpel-forming region, which is consistent with a role of this gene in floral transition and carpel and fruit development. Expression pattern of VAP1 suggests that it may play a role in flowering transition and flower development. However, its lack of expression in sepal primordia, does not support its role as an A-function gene in grapevine. Neither VFUL-L nor VAP1 expression was detected in vegetative organs such as leaves or roots. In contrast, they are expressed throughout tendril development. Transcription of both genes in tendrils of very young plants that have not undergone flowering transition indicates that this expression is independent of the flowering process. These unique expression patterns of genes typically involved in reproductive development have implications on our understanding of flower induction and initiation in grapevine, on the origin of grapevine tendrils and on the functional roles of AP1-and FUL-like genes in plant development. These results also provide molecular support to the hypothesis that Vitis tendrils are modified reproductive organs adapted to climb.

Genome-Wide Analysis of MIKCC-Type MADS Box Genes in Grapevine

“…Interestingly, the expression analyses performed for the entire MIKC family showed that only the two previously analyzed genes VvFUL-L and VvAP1 were highly expressed in tendrils, while VvFUL was highly expressed in latent buds and during flower meristem initiation and flower development. The early and high expression of VvFUL in latent buds during flowering transition suggests a role in this process, as has been proposed for VvAP1 and VvFUL-L based on in situ hybridization experiments (Calonje et al, 2004). This is consistent with the role proposed for AP1 and FUL in the specification of inflorescence and flower meristem identity in Arabidopsis (Mandel and Yanofsky, 1995;Ferrándiz et al, 2000a).…”

“…The second expression cluster included three major expression groups. The first group (VvAP1, VvFUL-L, and VvFUL) corresponded to genes expressed in tendrils and during flower meristem initiation and flower development, in agreement with their previously described expression patterns (Calonje et al, 2004). The second group corresponded to genes expressed during the differentiation of the outer flower whorls, including VvFLC1 and VvFLC2.…”

“…Two MIKC genes belonging to the AP1/FUL subfamily, VvAP1 and VvFUL-L, were previously shown to be expressed in the grapevine tendril, supporting its consideration as a sterile reproductive organ (Calonje et al, 2004). Our genomic survey of MIKC genes allowed the identification of a third member of this subfamily, VvFUL, which was identified as the closest FUL homolog (Supplemental Fig.…”

“…This has been the case for several members of the AP1/FUL, AP3/PI, AG, AGL6, SEP, and SOC1 subfamilies (Boss et al, 2001(Boss et al, , 2002Calonje et al, 2004;Poupin et al, 2007). Based on the availability of the grapevine genome sequence (Jailló n et al, 2007;Velasco et al, 2007), we report here a thorough unbiased identification and analysis of grapevine MIKC genes.…”

Relationship between Floral Development and Transcription Levels of LEAFY and TERMINAL FLOWER 1 Homologs in Japanese Pear (Pyrus pyrifolia Nakai) and Quince (Cydonia oblonga Mill.)

“…Several flowering-related genes, including LFY, TFL1, and AP1 homologs, have been isolated from grapevine (Vitis vinifera L.), citrus (Citrus sinensis Osbeck), kiwifruit (Actinidia deliciosa C. F. Liang & A. R. Ferguson), and apple (Malus domestica Borkh.) (Boss et al, 2001(Boss et al, , 2006Calonje et al, 2004;Carmona et al, 2002;Jeong et al, 1999;Joly et al, 2004;Kotoda et al, 2000Kotoda et al, , 2002Kotoda and Wada, 2005;Pillitteri et al, 2004;Sung et al, 1999Sung et al, , 2000Wada et al, 2002;Walton et al, 2001). We previously isolated and compared LFY and TFL1 homologs from six maloid fruit trees, including Japanese pear and quince, to elucidate the molecular basis of the differences in inflorescence architecture (Esumi et al, 2005); however, the derived amino acid sequences differed only slightly in their primary structures.…”