China Agricultural University researchers reveal how sugar transporters govern pollen wall formation and male fertility in maize
KeAi Communications Co., Ltd.
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Researchers identified two anther-specific hexose transporters, ZmSWEET6a and ZmSWEET6b, which synergistically regulate sugar homeostasis, primexine assembly, and redox balance during maize pollen development. The simultaneous loss of both transporters results in complete male sterility.
view moreCredit: Weiwei Jin,Wei Huang, et al.
Maize (Zea mays L.) is the primary grain crop in China with the largest planting area and highest total yield. It also serves as a model crop for the utilization of heterosis. Hybrid seed production is a core component in ensuring stable and high yields of maize, and the use of male-sterile lines has significantly improved breeding efficiency.
The pollen wall is a critical structure that protects pollen from environmental stresses, and its formation begins with a polysaccharide-rich primexine layer deposited on the surface of microspores. Proper pollen wall development is essential for male fertility in maize. In recent years, a large number of male-sterility genes have been successfully cloned in maize; however, the roles of sugar-related genes in male gametophyte development remain relatively underexplored. In particular, the molecular mechanisms by which sugar metabolism genes regulate pollen wall formation remain poorly understood.
To address this knowledge gap, a research team led by Professors Weiwei Jin and Wei Huang from China Agricultural University, in collaboration with Tianjin Agricultural University and the University of São Paulo in Brazil, elucidated how two anther-specific plasma membrane hexose transporters, ZmSWEET6a and ZmSWEET6b, coordinately regulate pollen wall development and cellular homeostasis. The study has been published online in The Crop Journal.
“We found that ZmSWEET6a/6b begin to play critical roles at early stages of microspore development, particularly during their peak expression window at stages S5–S6, when they supply essential polysaccharide precursors for primexine synthesis,” says Huang. “In addition to mediating transmembrane sugar transport, ZmSWEET6a/6b also maintain sugar–redox homeostasis in the anther, preventing premature ROS burst and ectopic initiation of PCD.”
How, then, do these sugar transporters simultaneously influence both pathways? Through cytological observations and multi-omics analyses, the research team constructed a coordinated regulatory model linking sugar transport, ROS signaling, and pollen wall development. Specifically, loss of ZmSWEET6a/6b function disrupts sugar homeostasis, triggering two cascading consequences: on one hand, pectin and xylan fail to deposit properly, leading to the collapse of primexine scaffold assembly; on the other hand, ROS burst occurs prematurely as early as stage S6 (whereas significant accumulation in the wild type occurs at stage S10), initiating ectopic and premature PCD across all four anther wall layers and ultimately resulting in complete male sterility.
“Deciphering the spatiotemporal coupling of carbohydrate metabolism and reproductive development is of great importance,” says Jin. “We hope this study offers new perspectives on the integration of metabolic and developmental pathways during plant reproduction.”
In summary, this study redefines ZmSWEET6a and ZmSWEET6b as central coordinators of anther development, revealing the dual role of sugar transporters in reproductive development—as suppliers of structural materials for pollen wall assembly and as guardians of anther redox balance.
“These findings not only deepen our understanding of how carbohydrate allocation regulates reproductive success in plants but also provide valuable genetic resources for the development of novel male-sterile lines in hybrid crop breeding,” says Jin.
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Contact the author: Wei Huang, Email address: wilsonhuang23@cau.edu.cn, Official website: https://www.sciencedirect.com/journal/the-crop-journal
The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 200 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).
Journal
The Crop Journal
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Hexose transporters ZmSWEET6a/6b are essential for primexine formation and redox homeostasis in maize anthers
New semi-dwarfing gene Sdd1 offers additional genetic resource for wheat architecture improvement
KeAi Communications Co., Ltd.
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The wheat mutant AS34 displays reduced plant height, compact spikes and altered stem cell morphology compared with wild type LK906.
view moreCredit: Professor Jie Liu, et al.
The Green Revolution of the 20th century transformed global wheat production, largely through the introduction of semi-dwarfing genes that reduced plant height, minimized lodging risk, and allowed for more nitrogen fertilizer use. Yet modern breeding remains heavily dependent on a limited set of these genes, some of which carry trade-offs in early seedling vigour, grain filling, and nitrogen-use efficiency.
Now, international research teams led by China Agricultural University and the Chinese Academy of Agricultural Sciences have identified and cloned a new semi-dwarfing gene, Sdd1 (semi-dwarf and dense-spike 1), that modulates plant height and spike architecture through a distinct hormonal balancing mechanism—offering breeders a fresh genetic resource to fine-tune wheat architecture.
The work builds on the team’s 2023 Nature report (Song et al., 2023, Nature. 617:118-124), which described a naturally occurring r-e-z large fragment deletion haploblock that promotes compact, semi-dwarf growth by rebalancing brassinosteroid and gibberellin signalling. In the new study, the researchers set out to find additional dwarfing genes operating independently of the r-e-z deletion background. Their search led them to AS34, a somatic mutant derived from the wheat line Lankao 906 (LK906, also known as Yumai 66), which harbors the r-e-z deletion haploblock.
In field trials, AS34 plants were just 45 cm tall on average—a notable 41.6% reduction compared with the 77 cm height of the wild-type LK906. In particular, the mutant’s spike length reduced by 44.0%, while spikelet density surged by 60.3%. Microscopic analysis revealed that stem cells in AS34 were shorter and broader than those in LK906, pointing to reduced longitudinal cell elongation as the cellular basis for the dwarf phenotype.
Genetic dissection placed the semi-dwarf and dense-spike traits under the control of a single major locus on chromosome 3B. Through fine-mapping with a segregating population, whole-genome resequencing, and newly developed molecular markers, the team pinpointed Sdd1 to a 5.7-Mb interval and identified TraesCS3B02G260400, encoding a small protein with function yet to be characterized, as the prime candidate gene. Independent mutant lines carrying distinct lesions in this gene—in the Jing 411 genetic background—all showed alterations in plant height and spike development, providing strong genetic confirmation of Sdd1’s regulatory role.
Hormone response assays added another layer of insight. Unlike LK906, AS34 showed enhanced sensitivity to gibberellin and auxin. This pattern suggests that Sdd1 does not act through a single hormone pathway but rather orchestrates cross-talk among multiple growth-regulating signals—a feature that may help decouple height reduction from negative side effects.
“Our earlier work demonstrated that the r-e-z fragment deletion improves plant architecture, increases grain weight, and boosts yield, mainly through the modulation of brassinosteroid and gibberellin,” says corresponding author of the study, Professor Jie Liu from China Agricultural University. “By identifying and cloning Sdd1—which remains fully functional in the r-e-z-deleted background—we’ve expanded the molecular framework for understanding how dwarfing genes wire into wheat developmental networks.”
Liu further elaborates on the distinct mechanism uncovered in this study, “What excites us is that, while the r-e-z deletion primarily influences brassinosteroid and gibberellin pathways, Sdd1 integrates multiple hormone signals in a more complex manner.”
The researchers further observed that AS34 mutants show dramatically reduced sensitivity to brassinosteroid but enhanced responses to both gibberellin and auxin. “This distinctive hormonal signature suggests Sdd1 occupies a unique node in the plant’s growth regulatory network,” adds Liu.
This feature may be particularly valuable for wheat breeding because it could help break the negative correlations that often accompany height reduction, such as reduced grain filling or compromised seedling vigor, usually caused by the largely blocked gibberellin signaling transduction.
“One of the most important aspects of this discovery is that Sdd1 remains fully functional in the r-e-z-deleted background,” emphasizes Liu. “This means we’ve identified a gene that can additively or synergistically interact with existing dwarfing resources.”
For breeders, this opens up new possibilities for stacking beneficial alleles to achieve optimal plant architecture without the trade-offs that have constrained the use of our current dwarfing gene toolbox.
Looking ahead, Liu outlines the next steps for the research, “We are only at the beginning of understanding its full potential. The protein encoded by TraesCS3B02G260400 is small and its molecular function remains to be characterized. We are now focusing on deciphering its mechanistic details—how it perceives or transmits hormonal signals, and what downstream target components it regulates.”
“Cloning Sdd1 is just the first step. Considerable work lies ahead to decipher its molecular function and clarify how it regulates growth and development,” adds Professor Xingguo Ye from the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, who co-led the research. “We are now focused on evaluating its practical breeding potential across different genetic backgrounds and environments to determine how broadly useful this gene might be for wheat improvement worldwide.”
The study also benefited from conceptual guidance and manuscript preparation input from Professors Qixin Sun and Zhongfu Ni from China Agricultural University. “With Sdd1 now in hand, breeders have a promising new entry point for designing wheat varieties that strike an optimal balance between height reduction, spike compactness, and overall productivity—without the constraints of the current dwarfing-gene toolbox,” says Ni.
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Contact contacts:
Professor Jie Liu
China Agricultural University
Professor Xingguo Ye
Institute of Crop Sciences, Chinese Academy of Agricultural Sciences
The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 200 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).
Journal
The Crop Journal
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Map-based cloning and functional analysis of the semi-dwarf and dense-spike gene Sdd1 in bread wheat
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