Starch function in ornamental tobacco floral nectary development

Functional Study of Transcription Factor MYB305 in Tobacco Flower Development

“…The development of ornamental tobacco flowers can be divided into 12 different stages (Koltunow et al, 1990). very high levels, reaching a peak amount about 24 hours before anthesis (Ren, 2007;Ren et al, 2007a;Ren et al, 2007c). Thereafter, starch is degraded rapidly and is converted to sugars for nectar production (Ren et al, 2007c) and as substrates for antioxidants (Horner et al, 2007).…”

“…The ornamental tobacco nectary is amyloplast type nectary and quantification study of ornamental tobacco nectary starch revealed that there is very little starch at an early flower developmental stage, soon thereafter the amount of starch increased dramatically, reaching a peak approximately 24 hours prior to anthesis (Horner et al, 2007;Ren et al, 2007c). During the last 24 hours before anthesis, the amount of starch decreased rapidly, and the accumulated starch is converted to sugars (sucrose, glucose and fructose) for nectar production prior to anthesis (Ren, 2007).…”

“…Most starch anabolic genes, including AGP and SS, are expressed in early stages, and are down regulated at the late stages. In contrast, starch catabolic genes, such as isoamylase (ISA), AAM and BAM, are not expressed at early stages, but are robustly expressed at late floral stages (Ren, 2007;Ren et al, 2007b). As a result, the starch accumulated in early stages is rapidly degraded to provide soluble carbohydrates for nectar secretion at late stages before anthesis.…”

“…The pigment responsible for the orange coloration is β-carotene (Horner et al, 2007). It has been proposed that the biosynthesis of βcarotene is governed by availability of substrate molecules arising from starch breakdown (Horner et al, 2007;Ren, 2007). The direct comparison of wildtype and…”

“…In the photosynthetic tissues, transient starch granules are synthesized in the chloroplasts during the day by capturing glucose made through photosynthesis and are degraded at night to provide sugars for other biological processes (Zeeman et al, 2002;Smith et al, 2005). In some nonphotosynthetic tissues, termed as sink organs, starch is synthesized in a form of storage starch in the amylosplasts (Ren, 2007). This storage starch accumulates to high levels and forms a reserve source of metabolites and energy for later use (Bieleski, 1995;Fernie et al, 2002).…”