Iron (Fe) deficiency is harmful to growth and development of plants. Plants can sense Fe deficiency conditions and modulate the expression of Fe deficiency responsive genes in order to maintain Fe homeostasis. POPEYE (PYE) was characterized as a negative regulator of the Fe homeostasis associated genes. However, the mechanism by which PYE regulates Fe homeostasis remains unclear.
In a study published in Journal of Experimental Botany, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) revealed that the PYE negatively regulated bHLH Ib genes in two different manners and the conditional nuclear localization of PYE was crucial for Fe homeostasis.
To further investigate the functions of PYE in the Fe deficiency response, the researchers constructed PYE overexpressing plants (PYEox). The results showed that PYE overexpression disrupted the Fe deficiency response. PYE negatively affected the expression of Fe homeostasis associated genes. PYE directly repressed the transcription of bHLH Ib genes (bHLH38, bHLH39, bHLH100, and bHLH101) by associating with their promoters.
Subcellular localization analysis indicated that PYE localized in both the cytoplasm and nucleus. PYE contained a Nuclear Export Signal (NES) which is required for the cytoplasmic localization of PYE. Mutation of the NES amplified the repression function of PYE, resulting in downregulation of Fe deficiency responsive genes.
Co-expression assays indicated that three bHLH IVc members (bHLH104, bHLH105/ILR3, and bHLH115) facilitated the nuclear accumulation of PYE. Conversely, PYE indirectly repressed transcription activation ability of bHLH IVc. Additionally, PYE directly negatively regulated its own transcription.
“Our study provides insights into the complicated Fe deficiency response signaling pathway and enhances the understanding of PYE functions,” said LIANG Gang of XTBG.
Contact
LIANG Gang Ph.D Principal Investigator
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China
E-mail: lianggang@xtbg.ac.cn
