Wheat NAC019 regulates kernel weight and quality

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Gao et al. demonstrate TaNAC019 regulates kernel weight and quality in wheat. The Plant Cell (2021). http://bit.ly/3qCTXSH

By YJ Gao, KX An, WW Guo, YM Chen, RJ Zhang, X Zhang, SY Chang, V Rossi, FM Jin, XY Cao, MM Xin, HR Peng, ZR Hu, WL Guo, JK Du, ZF Ni, QX Sun, and YY Yao

Background: Wheat flour is used to produce a wide range of products, such as leavened and unleavened breads, steamed buns, noodles, pancakes, cakes, and cookies. In wheat (Triticum aestivum L.) breeding, efforts have focused on improving both grain yield and quality. The content and composition of seed storage proteins (SSPs) are the target for quality improvements, as they determine the elasticity of wheat dough and flour processing quality. Starch levels in seeds are themselves associated with yield. However, improving flour quality generally comes at the expanse of yield, thus hindering the development of high-yielding wheat cultivars with good flour quality.

Question: We wanted to know which regulators coordinate SSP and starch accumulation in wheat grain. We explored the role of the endosperm-specific NAC transcription factor TaNAC019 in coordinating SSP and starch accumulation.

Findings: We determined that TaNAC019 binds to the promoters of TaGlu-1 loci, encoding high molecular weight glutenins (HMW-GS), as well as starch metabolism genes. The genetic inactivation of TaNAC019 by genome editing resulted in reduced transcript levels for all SSP types and genes involved in starch metabolism, leading to lower gluten and starch contents, as well as lower flour processing quality parameters. TaNAC019 directly activated the expression of HMW-GS genes by binding to a specific motif in their promoters and interacting with the TaGlu-1 regulator TaGAMyb. TaNAC019 also indirectly regulated the expression of TaSPA, an ortholog of maize Opaque2 that activates SSP accumulation. Therefore, TaNAC019 regulation of starch- and SSP-related genes has key roles in wheat grain quality. Finally, we identified an elite allele (TaNAC019-BI) associated with flour processing quality, providing a promising candidate gene for breeding wheat with improved quality.

Next steps: Wheat breeders aim to improve grain yield and quality. Our work demonstrates that TaNAC019 is an excellent candidate for developing wheat cultivars with both high yield and good quality. The TaNAC019-BI allele represents a genetic marker that may be used in marker-assisted breeding programs.

Article:

Yujiao Gao, Kexin An, Weiwei Guo, Yongming Chen, Ruijie Zhang, Xue Zhang, Siyuan Chang, Vincenzo Rossi, Fangming Jin, Xinyou Cao, Mingming Xin, Huiru Peng, Zhaorong Hu, Weilong Guo, Jinkun Du, Zhongfu Ni, Qixin Sun, Yingyin Yao (2021). The endosperm-specific transcription factor TaNAC019 regulates glutenin and starch accumulation and its elite allele improves wheat grain quality. The Plant Cell, http://bit.ly/3qCTXSH