Spatio-Temporal Dynamics of Fructan Metabolism in Developing Barley Grains

Abstract

Barley (Hordeum vulgare) grain development follows a series of defined morphological and physiological stages and depends on the supply of assimilates (mainly sucrose) from the mother plant. Here, spatio-temporal patterns of sugar distributions were investigated by mass spectrometric imaging, targeted metabolite analyses, and transcript profiling of microdissected grain tissues. Distinct spatio-temporal sugar balances were observed, which may relate to differentiation and grain filling processes. Notably, various types of oligofructans showed specific distribution patterns. Levan-and graminan-type oligofructans were synthesized in the cellularized endosperm prior to the commencement of starch biosynthesis, while during the storage phase, inulin-type oligofructans accumulated to a high concentration in and around the nascent endosperm cavity. In the shrunken endosperm mutant seg8, with a decreased sucrose flux toward the endosperm, fructan accumulation was impaired. The tight partitioning of oligofructan biosynthesis hints at distinct functions of the various fructan types in the young endosperm prior to starch accumulation and in the endosperm transfer cells that accomplish the assimilate supply toward the endosperm at the storage phase.

Soluble carbohydrates in developing and mature diaspores of polar Caryophyllaceae and Poaceae

“…In our previous study, short-term exposure to cold stress stimulated the accumulation of 1-kestose in shoots of D. antarctica and Poa arctica plants (Pastorczyk et al 2014). Peukert et al (2014) Table 2). Mean ± SE (n = 3).…”

“…In the generative phase and during kernel development, fructans synthesized and accumulated in shoots are remobilized to supply kernels with additional sucrose (Amiard et al 2003;Zhang et al 2015). Fructans (like 1-kestose) present in immature kernels are used up during starch synthesis during reserve accumulation (Verspreet et al 2013;Peukert et al 2014). In mature cereal kernels, 1-kestose (a-D-glucopyranosyl-(1 ?…”

Linking Expression of Fructan Active Enzymes, Cell Wall Invertases and Sucrose Transporters with Fructan Profiles in Growing Taproot of Chicory (Cichorium intybus): Impact of Hormonal and Environmental Cues

“…Fructan metabolism has been linked to plant adaption to abiotic stresses (Livingston et al, 2009). In particular, small oligofructans may serve as osmolytes in maintaining osmotic homeostasis, provide direct protection of phospholipid membranes, and act as scavengers of reactive oxygen species (Van den Ende et al, 1998; Valluru and Van den Ende, 2008; Peukert et al, 2014). The strong but transient increase of VI transcript abundance ( Figure 4 ) in leaf blade and taproot may affect vacuolar sucrose/hexose ratio, thereby contributing to osmotic adjustment as part of an ABA-induced stress response.…”

“…Inulin is degraded by fructan 1-exohydrolase, in chicory being encoded by three isoforms, namely 1-FEH1, 1-FEH2a and 1-FEH2b. Noteworthy, short chain oligofructans such as kestose and nystose may also be hydrolyzed by acid invertases (Peukert et al, 2014). …”

Metabolic architecture of the cereal grain and its relevance to maximize carbon use efficiency

“…Toward this end, various approaches have been successfully applied, e.g. mass spectrometry imaging (Peukert et al, 2014) and laser microdissection-coupled analytics (Schiebold et al, 2011;Belmonte et al, 2013). While such approaches can provide an excellent level of static chemical and/or spatial resolution, it is invasive and thus has only limited ability to generate dynamic measurements.…”