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Accueil du site → Doctorat → Australie → 2020 → Sucrose transporter genes for efficient remobilization of stem water soluble carbohydrate to grain in wheat under different environments.

Murdoch University (2020)

Sucrose transporter genes for efficient remobilization of stem water soluble carbohydrate to grain in wheat under different environments.

Al-Sheikh Ahmed, Sarah Meqdam Taha

Titre : Sucrose transporter genes for efficient remobilization of stem water soluble carbohydrate to grain in wheat under different environments.

Auteur : Al-Sheikh Ahmed, Sarah Meqdam Taha

Université de soutenance : Murdoch University

Grade : Doctor of Philosophy (PhD) 2020

Résumé partiel
Wheat is one of the largest crops in the world with annual production of around 600 million tonnes. About 24 million tonnes of wheat is produced in Australia under rain-fed conditions and almost 80% of those is exported to overseas. Australia is experiencing climate change with increased incidence and severity of droughts and declining winter rainfall in areas with Mediterranean climate. Stem water soluble carbohydrate (WSC) deposited in wheat stems represent an important carbon sources for grain filling, especially under terminal drought conditions. Sucrose is the major transportable form of carbon in plants and the sucrose transporter (SUT) gene family is important in facilitating phloem loading and unloading. This PhD explores SUT functions on stem WSC remobilization under two environmental constraints, drought and nitrogen (N) supply in two wheat cultivars, Westonia and Kauz. It also examines diurnal changes in gene expression and WSC remobilization.

Firstly, to determine the major functional SUT gene groups in the shoot of wheat during grain development, drought tolerant varieties, Westonia and Kauz, were investigated in field drought experiments. The homologous genes to OsSUT1-5 were identified in Westonia and Kauz, namely TaSUT1_4A, TaSUT1_4B, TaSUT1_4D ; TaSUT2_5A, TaSUT2_5B, TaSUT2_5D ; TaSUT3_1A, TaSUT3_1D ; TaSUT4_6A, TaSUT4_6B, TaSUT4_6D ; TaSUT5_2A, TaSUT5_2B, and TaSUT5_2D. TaSUT1-5 gene expression patterns in stem, leaf sheath, rachis, lemma and developing grain were explored from pre-anthesis to grain maturity. TaSUT1 was the major sucrose transporting group in all studied organs and the expression was particularly higher in grain. TaSUT3 was preferentially expressed in the lemma before anthesis thus, it is hypothesised that it may contribute to pollination and seed setting. TaSUT5 was weakly expressed in developing grain while it was not expressed in other tissues.

Secondly, the effects of drought on expression of SUT in wheat under well-watered and drought conditions during grain filling are unknown. Plants were harvested from pre-anthesis to grain maturity, and the stem and developing grain were used for analysing TaSUT gene expression. The upregulation of TaSUT1 in Westonia in the stem and grain suggest a crucial role for the remobilization of stem WSC to grain under drought. Also, TaSUT1 gene expression was significantly correlated with high total grain weight (TGW) in Westonia under drought stress. In Kauz, the significant correlations between TaSUT1 gene expression and TGW and kernel number per spike demonstrated the contribution of TaSUT1 to high grain yield in an irrigated environment. Thus, efficient stem WSC remobilization to grain under drought should enhance grain yield.

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