Abstract

BackgroundAFP is a negative regulator of ABA signaling that promotes ABI5 protein degradation and weakens regulation of ABA signaling by targeting upstream genes of ABI5, and TaABI5 gene was seed-specific, and accumulated during wheat grain maturation and dormancy acquisition, which played an important role in seed dormancy; TaAFP has a conserved domain with AFP, so TaAFP may also play an important role in seed dormancy in wheat.ResultsTwo allelic variants of TaAFP were identified on chromosome 2BS in common wheat, and designated as TaAFP-B1a and TaAFP-B1b. Sequence analysis showed a 4-bp deletion in the 5’UTR region of TaAFP-B1b compared with TaAFP-B1a. Based on the 4-bp deletion, a co-dominant functional marker of TaAFP-B was developed and designated as AFPB. The genotype generating a 203-bp fragment (TaAFP-B1b) was more resistant to pre-harvest sprouting than the genotype producing a 207-bp fragment (TaAFP-B1a) in a test of 91 white-grained Chinese wheat cultivars and advanced lines. The average germination index(GI) values of TaAFP-B1a and that of TaAFP-B1b were 45.18 and 30.72%, respectively, indicating a significant difference (P < 0.001). Moreover, the 4-bp deletion located in the 5’UTR not only affected the transcription level of TaAFP-B but also affected the mRNA decay, reduced the translation level of GUS and tdTomatoER and GUS activity in wheat leaves of transient expression. The transcript expression and the mRNA half-life value of TaAFP-B1a in developing seeds and mature seeds were much higher than those of TaAFP-B1b.ConclusionWe identified a 4-bp InDel in the 5’UTR of TaAFP-B, which affected the mRNA transcription level, mRNA decay, translation levels of GUS and tdTomatoER, GUS activity, and was significantly associated with seed dormancy in common wheat. A functional marker was developed and validated based on this InDel.

Highlights

  • AFP is a negative regulator of abscisic acid (ABA) signaling that promotes ABI5 protein degradation and weakens regulation of ABA signaling by targeting upstream genes of ABI5, and TaABI5 gene was seed-specific, and accumulated during wheat grain maturation and dormancy acquisition, which played an important role in seed dormancy; Three wheat AFP genes (TaAFPs) has a conserved domain with AFP, so TaAFP may play an important role in seed dormancy in wheat

  • TaAFP-A1a and TaAFP-A1b were on chromosome 2AS; TaAFP-B1a and TaAFP-B1b were on chromosome 2BS; and TaAFP-D1a and TaAFP-D1b were on chromosome 2DS

  • The most abundant TaAFP-B transcript levels in Zhou 8425B and Wanxianbaimaizi were detected at 20 days after pollination (DAP), while the highest transcriptional level of TaABI5 occurred at 20 DAP in Zhou 8425B and at 30 DAP in Wanxianbaimaizi (Fig. 4). These results indicated that the time of the highest transcription level of TaABI5 was latter than that of TaAFPB in Wanxianbaimaizi; this might be another reason why Wanxianbaimaizi has a higher capacity of seed dormancy than Zhou 8425B

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Summary

Introduction

AFP is a negative regulator of ABA signaling that promotes ABI5 protein degradation and weakens regulation of ABA signaling by targeting upstream genes of ABI5, and TaABI5 gene was seed-specific, and accumulated during wheat grain maturation and dormancy acquisition, which played an important role in seed dormancy; TaAFP has a conserved domain with AFP, so TaAFP may play an important role in seed dormancy in wheat. A high level of seed dormancy plays a pivotal role in resistance to pre-harvest sprouting (PHS), providing a mechanism for plants to delay germination until conditions are optimal for survival of the generation [1, 2]. The mechanism of ABA sensitivity in seeds has been extensively studied in Arabidopsis. Some genes associated with seed dormancy have been identified as factors in the ABA signaling and ABA synthesis. ABI5 binding protein (AFP), a novel negative regulator of ABA signaling that works by facilitating the degradation of ABI5 [18], was isolated using yeast two-hybrid assays; AFP functions in developing seeds and young seedlings [18]. ABI5 acts as a critical factor in maturation, dormancy development of seeds, or the dehydration tolerance of young seedlings of Arabidopsis [19, 20]

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