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Nexine is an essential layer of the pollen wall. TRANSPOSABLE ELEMENT SILENCING VIA AT-HOOK (TEK), a member of the AT-HOOK MOTIF CONTAINING NUCLEAR-LOCALIZED (AHL) family, is a key regulator for nexine formation in Arabidopsis. In this study, we report that TEK interacts with TEOSINITE BRANCHED1-CYCLOIDEA-PCF 14 (TCP14) and TCP15 to regulate nexine formation. TCP14/15 are expressed in the anther cell layers including the tapetum. Although tcp14 tcp15 has no anther development defect, specifically repressing TCP15 and its homologs during the nexine formation stage in the pAMS::TCP15-SRDX transgenic plants leads to a defect in the nexine layer and complete sterility. Cell wall and other pollen wall formation-related genes are significantly enriched among downregulated genes in the transgenic line. This indicates that TCP14/15 and other TCP members are required for nexine formation. In addition, tek exhibits thermosensitive genic male sterility (TGMS) as its fertility was partially restored under low temperature (17°C), suggesting other AHL family members play a redundant role in nexine formation. AHL8 is localized in the tapetum and interacts with TCP14 and TCP15. Although the fertility of the ahl8 tek double mutant is similar to tek under 17°C, dominant suppression of AHL homologs in pAMS::AHL8-SRDX transgenic plants exhibits complete male sterility under 17°C. All these indicate that AHL8 and other AHLs play a redundant role in interacting with TCPs to regulate nexine formation. This work not only reveals the regulatory mechanism for nexine formation, but also provides a novel thermosensitive genic male sterile (TGMS) locus that may have potential applications in agriculture.
Xiong et al. (Sat,) studied this question.