Abscisic acid delays chickpea germination by inhibiting water uptake and down-regulating genes encoding cell wall remodelling proteins

Abstract

Here, we compare the germination of chickpea seeds when they were imbibed in mannitol and in ABA. Radicle protusion was delayed by both treatments, however, while the negative effect of mannitol, which severely reduced earlier water uptake, was reversed after 24 h of treatment, this was not the case of ABA, indicating a specific effect of the hormone. Since germination depends not only on the water content but also on cell wall extensibility, we analyzed the rate of transcription of some genes encoding cell wall remodelling proteins, known to be involved in chickpea germination, in embryonic axes excised from seeds imbibed in mannitol or in ABA. Our results show that ABA and mannitol modify their transcription patterns. Among the a-expansins, the proteins encoded by CaEXPA-3 and CaEXPA-4 must be responsible for the germination observed in mannitol-treated seeds, because their transcripts appeared earlier on in mannitol than in ABA-treated seeds. Moreover, it may further be concluded that CaXTH-1 is one of the genes able of transcription in very low hydrated seed.