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Journal of Integrative Agriculture
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SbNAC22 coordinates starch biosynthesis in sorghum grain by regulating pathway related functional genes

Min Yin1, Yi Zheng1, Haotong Zeng1, Zheyu Yan1, Anqi Sun1, Kuang Ma1, Xiangling Gong1, Jing Li1, Qianlin Xiao1, 2#, Zhizhai Liu1, 2#

1 College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China

2 Chongqing Key Laboratory of Crop Molecular Improvement, Chongqing 400715, China

 Highlights 

A NAC-family transcription factor of SbNAC22 with self-activating was profiled to regulate the transcription of multiple starch biosynthesis related genes by binding to the NAC-specific cis-elements.

Over-expressed SbNAC22 in rice line of Zhonghua 11 caused enhanced grain length and weight, as well as significantly increased total starch content in the grains.

Integrated results of both sorghum and rice implied that SbNAC22 could transactivate SbAGPLS1, SbGBSSI, SbSSI, and suppress SbISA1, to regulate starch biosynthesis and accumulation in developing sorghum grains.

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摘要  

淀粉作为高粱籽粒的主要组分及关键利用成分,其含量主要受时空特异性表达的淀粉生物合成相关基因(SBRGs)调控,然而这些基因在高粱中的转录调控机制尚不明确本研究解析NAC型转录因子SbNAC22在高粱籽粒淀粉生物合成中的主要功能。结果显示,SbNAC22在高粱籽粒发育阶段特异高表达,并且与多个高粱SBRGs呈共表达趋势。蛋白特性分析结果表明,SbNAC22定位于细胞核,有自激活结构域并具自激活活性。DAP-seq、双荧光素酶分析、EMSA等研究结果显示,SbNAC22可以与保守基序5’-CACGCAA-3’结合,进而影响携带该基序的高粱SBRGs的启动子活性。瞬时超表达研究发现,SbNAC22可以显著上调SbAGPLS1SbAGSSISbSSI等基因的表达,同时抑制SbISA1的转录。在水稻中异源超表达SbNAC22后,发现该转录因子对水稻同源基因存在相似的调控模式;同时还发现超表达株系籽粒变长,粒重增加,籽粒中的总淀粉含量极显著增加。综合本研究结果,我们初步明确了SbNAC22通过差异性激活与抑制SBRGs,成为调控高粱淀粉生物合成的关键转录因子。本研究表明NAC型转录因子SbNAC22,可以作为新型分子育种策略的重要靶点,应用于高粱籽粒产量与品质改良的育种实践



Abstract  

Starch, the predominant component in sorghum grains and a key component for utilization, is primarily regulated by spatiotemporally specific starch biosynthesis-related genes (SBRGs) with poorly characterized transcriptional mechanisms. This study elucidates the functional role of the NAC-type transcription factor (TF) SbNAC22 in starch biosynthesis in sorghum grains. SbNAC22 exhibits preferential expression levels in developing grains and demonstrates co-expression trends with multiple sorghum SBRGs. SbNAC22 possesses nuclear targeting, autoactivation activity, and intrinsic activity domain. The integrated results of DAP-seq, dual-luciferase analysis, and EMSA imply that SbNAC22 could bind to the conserved motif of 5-CACGCAA-3’, influencing the promoter activities of the corresponding SBRGs. Transient overexpression assays revealed that SbNAC22 can also upregulate critical SBRGs of SbAGPLS1, SbGBSSI, and SbSSI, while suppress SbISA1 in sorghum. Heterologous expression in rice further demonstrates the conserved regulatory capacity of SbNAC22, elevating transcript levels of rice SBRGs, enhancing grain length and weight, and significantly increasing the starch content in rice grains. The findings of this study identify SbNAC22 as a key transcriptional regulator that orchestrates starch biosynthesis by differentially activating and repressing SBRGs, positioning SbNAC22 as a prime target for novel molecular breeding strategies designed to enhance both grain yield and quality in sorghum.

Keywords:  starch biosynthesis       SbNAC22       transcriptional regulation       sorghum (Sorghum bicolor L.)  
Online: 31 December 2025  
Fund: 

This work was supported by the National Natural Science Foundation of China (32372076), the Fundamental Research Funds for the Central Universities (SWU-XDJH202315, SWU-KF25037), and the College Student Innovation and Entrepreneurship Training Program Project of Southwest University (202510635102).

About author:  #Correspondence Qianlin Xiao, E-mail: xiaoql1853@swu.edu.cn; Zhizhai Liu, E-mail: liu003@swu.edu.cn

Cite this article: 

Min Yin, Yi Zheng, Haotong Zeng, Zheyu Yan, Anqi Sun, Kuang Ma, Xiangling Gong, Jing Li, Qianlin Xiao, Zhizhai Liu. 2025. SbNAC22 coordinates starch biosynthesis in sorghum grain by regulating pathway related functional genes. Journal of Integrative Agriculture, Doi:10.1016/j.jia.2025.12.079

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