Functional Approaches to Study Leaf Senescence in Sunflower

FERNANDEZ , P.; MOSCHEN, S.; PANIEGO, N.B.; HEINZ, R.A.

Senescence

InTech

Año: 2012; p. 69 - 88

Senescence is an age-dependent process at the cellular, tissue, organ or organism level, leading to death of the end of the life span (Noodén, 1988). In this context, not only environmental but also biotic factors influence  senescence, being this an irreversible process prematurely induced under these unfavourable conditions (Lim et al., 2003). It have been documented that a delay in leaf senescence has an important impact on grain yield trough the maintenance of the photosynthetic leaf area during the reproductive stage in different crops (Thomas and Howart, 2000), including sunflower (Sadras et al., 2000; De la Vega et al., 2011). The onset and progression of senescence is accompanied by global changes in gene expression. Senescence Associated Genes (SAGs) has been extensively studied in model plant species (Gepstein et al., 2003; Balazadeh et al., 2008; Sarvepalli and Nath, 2011; Zhou et al., 2011); and in some agronomical relevant crops (Andersen et al., 2004; Uauy et al., 2006; Espinoza et al., 2007). Sunflower (Helianthus annuusL.) is one of the most relevant crops as a source of edible oil and many efforts have been achieved to build up useful functional genomics tools for cultivated sunflower involving transcriptional and metabolic profiles (Fernandez et al., 2003; Paniego et al., 2007; Fernandez et al., 2008; Peluffo et al., 2010). Although, molecular studies focused on the onset of the senescence  process in sunflower leaf are scarce (Fernandez et al., 2003; Jobit et al., 2007; Paniego et al., 2007; Fernandez et al., 2008; Peluffo et al., 2010; Fernandez et al., 2011). Considering that even when there are ongoing initiatives for Sunflower Genome Sequencing (http://www.sunflowergenome.org/), the lack of these sequences at the present limits concerted transcriptional approaches to dissect the senescence process and its role in keeping green leaf area to support photosynthetic activity. Thus candidate gene approach turns up as an alternative to primarily describe the molecular events occurring during leaf senescence which may be partially understood as a straight remobilization activity, among others. To aim this approximation, a literature revision based on described SAGs genes not only in model plant species but also in agronomical relevant crops with or without genomic information available will be covered by the review format chapter proposed. Concomitantly, the available information about physiological aspects associated to sunflower senescence at different developmental stages and at different growing conditions as well as updated functional genomics tools developed for this crop will be discussed in the proposed revision.