期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：36
DOI：10.1073/pnas.2121671119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Effective communication between source organs and sink organs is pivotal in carbohydrate assimilation and partitioning during plant growth and development. Auxin is required for many aspects of plant growth and development. However, very little is known about how these two important classes of molecules coordinate and co-regulate plant developmental processes. In this study, we elucidate an OsARF18-OsARF2-OsSUT1–mediated auxin signaling cascade regulating carbohydrate partitioning between the source and sink tissues in rice, which is essential for proper development of rice reproductive organs. Our findings represent a major step forward in increasing our knowledge of sucrose transport regulation in plants and have important implications in improving crop yield through better coordination of source and sink activities.
Carbohydrate partitioning between the source and sink tissues plays an important role in regulating plant growth and development. However, the molecular mechanisms regulating this process remain poorly understood. In this study, we show that elevated auxin levels in the rice
dao mutant cause increased accumulation of sucrose in the photosynthetic leaves but reduced sucrose content in the reproductive organs (particularly in the lodicules, anthers, and ovaries), leading to closed spikelets, indehiscent anthers, and parthenocarpic seeds. RNA sequencing analysis revealed that the expression of
AUXIN RESPONSE FACTOR 18 (
OsARF18) and
OsARF2 is significantly up- and down-regulated, respectively, in the lodicule of
dao mutant. Overexpression of
OsARF18 or knocking out of
OsARF2 phenocopies the
dao mutant. We demonstrate that OsARF2 regulates the expression of
OsSUT1 through direct binding to the sugar-responsive elements (SuREs) in the
OsSUT1 promoter and that OsARF18 represses the expression of
OsARF2 and
OsSUT1 via direct binding to the auxin-responsive element (AuxRE) or SuRE in their promoters, respectively. Furthermore, overexpression of
OsSUT1 in the
dao and
Osarf2 mutant backgrounds could largely rescue the spikelets’ opening and seed-setting defects. Collectively, our results reveal an auxin signaling cascade regulating source-sink carbohydrate partitioning and reproductive organ development in rice.
