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
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The Crop Journal
Experimental study
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Hexose transporters ZmSWEET6a/6b are essential for primexine formation and redox homeostasis in maize anthers
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.