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Deciphering heat wave effects on wheat grain: focusing on the starch fraction
Publication . Pereira, Rita; Tomás, Diana; Silva, Manuela
Wheat is an essential staple food, and its production and grain quality are affected
by extreme temperature events. These effects are even more relevant
considering the increasing food demand for a growing world population and
the predicted augmented frequency of heat waves. This study investigated the
impact of simulated heat wave (HW) conditions imposed during grain filling on
starch granule characteristics, endosperm ultrastructure, and transcriptomic
modulation of genes involved in starch synthesis and degradation. All these
evaluations were performed with four different genotypes, two commercial
wheat varieties (Antequera and Bancal), and two traditional landraces (Ardito
and Magueija). Starch granule size distribution and shape were significantly
altered by HW treatment, revealing an increase of A-type granules in Ardito
and an opposite effect in Magueija and Bancal, while Antequera remained stable.
Analysis of the largest (LD) and smallest (SD) granule diameters also revealed
genotype-specific changes, with Magueija showing a shift toward more spherical
A-type granules after the HW treatment. Scanning electron microscopy
confirmed alterations in endosperm morphology, including increased
vitreousness in Bancal and substantial increase of endosperm cavities and grain
size reduction in Magueija under HW stress. The transcriptomic analysis
confirmed the stability of Antequera under HW, in contrast with the other
genotypes where differential gene expression related to starch metabolism was
detected. These effects were particularly severe in Magueija with the
downregulation of genes encoding for enzymes involved in amylopectin
synthesis (both starch synthases and starch-branching enzyme) and
upregulation of a-amylase-encoding genes. These findings contribute to the
understanding of heat stress effects on wheat grain quality, emphasize the
importance of genetic diversity in HW responses, and suggest potential
avenues for breeding climate-resilient wheat varieties.
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Fundação para a Ciência e a Tecnologia
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OE
Número da atribuição
SFRH/BD/93156/2013