ACOS5Is Required For Primexine Formation And Sporopollenin Deposition On Microspores In Arabidopsis Thaliana

Pollen exine, mainly composed of sporopollenin, plays important roles during microspore development. It has been known that Acyl-CoA Synthetase5(ACOS5) is required for sporopollenin biosynthesis in Arabidopsis thaliana. However, whether ACOS5participates in primexine pattern formation remains uncharacterized. In this report, our study results showed that ACOS5is essential for primexine deposition during Arabidopsis microspore development. Through forward genetic screen, we identified a point mutation of ACOS5allele, acos5-2, showing abnormal microspore development. Microspores were degenerated and aborted after released from the tetrads. TEM observation showed that primexine formation was abnormal in acos5-2mutant. Consequently, sporopollenin was randomly deposited and aggregated on the microspores. RNA in situ hybridization indicated that expression of ACOS5relies on the function of DYT1and TDF1. Furthermore,593bp sequence promoter contains enough information to drive ACOS5expression in the anther. Our data provide evidence that ACOS5is required for primexine formation and sporopollenin deposition during pollen development.