A putative NAP homolog specifically expressed during grapevine flower and berry development

Abstract

Introduction: In flowering plants, fruit morphogenesis is a distinct and unique process following fertilization. Most fleshy fruits as grapevine develop from ovary tissues (EAMES and MACDANIELS 1947) and exhibit convergent characteristics such as pericarp cell proliferation and enlargement. The early molecular events that control the dynamics of fruit morphogenesis remain obscure. From preliminary analysis of the fleshless berry mutant (Vitis vinifera L. cv. Ugni Blanc) which is unable to specify ovary cell fate later in fleshy pericarp development, we have identified a gene homolog of PISTILLATA up-regulated in the mutant ovary. In Arabidopsis, NAP (AJ222713) appeared as an immediate target of the floral homeotic genes PISTILLATA/APETALA3 (SLABLOWSKI and MEYEROWITZ 1998). NAP genes belong to the NAC domain gene family encoding transcriptional regulators required for meristem establishment and other plant developmental processes. The original genes NO APICAL MERISTEM (NAM) from petunia, ATAF1, 2 and CUPSHAPED COTYLEDON (CUC2) from Arabidopsis defined the highly conserved NAC protein domain (AIDA et al. 1997). We report, here, quantitative expression patterns of the closest NAP grapevine homolog (TC38700 from the TIGR database), VvNAP, during grapevine development of the flb mutant and the wild type genotypes. Material and Methods: The flb mutation was identified in 1996 in a vineyard located at Prades-le-Lez (France) on a Vitis vinifera cv. Ugni-Blanc anticlinal chimeric plant bearing some shoots with berries dramatically reduced in size. For flb mutant and wild-type Ugni Blanc, samples corresponded to inflorescences from stage 17 (mature inflorescence with all flowers formed and separated) and 19 (first flower caps loosening) of the E-L system (COOMBE 1995) and berries from 0 to 20 d after anthesis collected in the greenhouse (ENSA.M-INRA, Montpellier). For V. vinifera cv. Cabernet-Sauvignon, samples corresponded to vegetative organs (young roots, shoot tips including 2 to 3 expanded leaves and young leaves), inflorescences from stages 7 (immature inflorescence emerging from buds) and 17, flowers at flowering time (50 % caps off) and seedless berries (2-16 weeks post flowering), harvested in the field (Clare Valley, Australia). Total RNA was extracted using RNeasy Plant Mini kit (Qiagen) for Ugni Blanc and according to REZAIAN and KRAKE (1987) with slight modifications as described in BOSS et al. (2001) for Cabernet-Sauvignon.