The role of NAC transcription factors in the genetic regulation of senescence timing and grain protein content in wheat

Evans, Catherine Emma Blessley ORCID: 0000-0001-7959-6721 (2024). The role of NAC transcription factors in the genetic regulation of senescence timing and grain protein content in wheat. University of Birmingham. Ph.D.

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Abstract

Wheat is the fourth most produced crop globally, and the first in the UK. High wheat grain protein content is important for both baking quality and nutritional value. A genetic trade-off between protein content and yield makes it a challenge to improve protein content without decreasing yield. In wheat, nitrogen remobilized from senescing leaves to developing grain contributes to grain protein content, and earlier leaf senescence correlates with increased protein and decreased yield. Transcription factors regulate the timing of leaf senescence in plants.
The aim of this thesis was to characterize the role of NAC transcription factors in regulating senescence timing in wheat. To achieve this, the progress of leaf and peduncle senescence was measured in wheat with overexpression or loss-of-function mutations of candidate NAC transcription factors. Results showed that NAC5-1 and NAM-2 promote earlier senescence, while NAP-1 does not. NAC5-1 and NAM-2 promote decreased grain length and kernel weight respectively, but do not affect grain protein content. This provides some support to the model that transcriptional regulation of senescence timing mediates the trade-off between wheat protein content and yield. Showing that NAC5-1 and NAM-2 regulate senescence timing contributes to deciphering the transcription factor network of senescence in wheat. To explore application of transcription factors regulating senescence to wheat breeding, this thesis demonstrated that known senescence regulator NAM-1 increases grain protein content in a UK field context. Allelic variants in candidate NAC transcription factors were identified and tracked in wheat breeding populations. Variation in senescence-regulating transcription factors such as NAC5-1 and NAM-2 could be targeted in wheat breeding to optimise the balance between wheat grain protein content and yield.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):