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IMPERFECTIVE EXINE FORMATION (IEF) is required for exine formation and male fertility in Arabidopsis

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IEF, a novel plasma plasma membrane protein, is important for exine formation in Arabidopsis.


Exine, an important part of pollen wall, is crucial for male fertility. The major component of exine is sporopollenin which are synthesized and secreted by tapetum. Although sporopollenin synthesis has been well studied, the transportation of it remains elusive. To understand it, we analyzed the gene expression pattern in tapetal microdissection data, and investigated the potential transporter genes that are putatively regulated by ABORTED MICROSPORES (AMS). Among these genes, we identified IMPERFECTIVE EXINE FORMATION (IEF) that is important for exine formation. Compared to the wild type, ief mutants exhibit severe male sterility and pollen abortion, suggesting IEF is crucial for pollen development and male fertility. Using both scanning and transmission electron microscopes, we showed that exine structure was not well defined in ief mutant. The transient expression of IEF-GFP driven by the 35S promoter indicated that IEF-GFP was localized in plasma membrane. Furthermore, AMS can specifically activate the expression of promoterIEF:LUC in vitro, which suggesting AMS regulates IEF for exine formation. The expression of ATP-BINDING CASSETTE TRANSPORTER G26 (AGCB26) was not affected in ief mutants. In addition, SEM and TEM data showed that the sporopollenin deposition is more defective in abcg26/ief-2 than that of in abcg26, which suggesting that IEF is involved in an independent sporopollenin transportation pathway. This work reveal a novel gene, IEF regulated by AMS that is essential for exine formation.

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taken from abcg26/ief-2 mutant anther at later stage. dPG degenerated pollen grain; En endothecium; ML middle layer; T tapetum. Bar = 1 µm. f High-magnification images showing pollen wall ultrastructure of aborted abcg26/ief-2 pollen grain. dPG degenerated pollen grain; In intine; Ne nexine; T tapetum. Bar = 1 µm

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We thank Haihan Wang for the assistance and Zaibao Zhang for revising the manuscript.


This work was supported by the National Natural Science Foundation of China (Grant Nos. 31900260; 30970268).

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XX and JG conceived and supervised the project; KW and XZ performed most of the experiments; CP performed the complementation experiment; XQ, SZ, NT and NY performed the Dual-luciferase transient expression assay; KW and XX wrote the manuscript; PX gave constructive comments on this work and revised the manuscript. All authors read and approved the final manuscript.

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Correspondence to Xiaofeng Xu or Jufang Gao.

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Accession numbers Sequence data from this article can be found in GenBank under the following

Accession numbers: TUB8 (At5g23860), IEF (At5g58100), AMS (At2g16910), ACOS5 (At1g62940), MS2 (At3g11980), CYP703A2 (At1g01280), CYP704B1 (At1g69500), PKSA (At1g02050), PKSB (At4g34850), TKPR1 (At4g35420), TKPR2 (At1g68540), SHT (At2g19070), ABCG26 (At3g13220), ARF17 (At1g77850), MYB33 (At5g06100), TDF1 (At3g28470)

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Wang, K., Zhao, X., Pang, C. et al. IMPERFECTIVE EXINE FORMATION (IEF) is required for exine formation and male fertility in Arabidopsis. Plant Mol Biol 105, 625–635 (2021).

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