SUMO E3 ligase AtMMS21 is required for normal meiosis and gametophyte development in Arabidopsis.

Background: MMS21 is a SUMO E3 ligase that is conserved in eukaryotes, and has previously been shown to be required for DNA repair and maintenance of chromosome integrity. Loss of the Arabidopsis MMS21 causes defective meristems and dwarf phenotypes.

Results: Here, we show a role for AtMMS21 during gametophyte development. AtMMS21 deficient plants are semisterile with shorter mature siliques and abortive seeds. The mms21-1 mutant shows reduced pollen number, and viability, and germination and abnormal pollen tube growth. Embryo sac development is also compromised in the mutant. During meiosis, chromosome mis-segregation and fragmentation is observed, and the products of meiosis are frequently dyads or irregular tetrads. Several transcripts for meiotic genes related to chromosome maintenance and behavior are altered. Moreover, accumulation of SUMO-protein conjugates in the mms21-1 pollen grains is distinct from that in wild-type.

Conclusions: Thus, these results suggest that AtMMS21 mediated SUMOylation may stabilize the expression and accumulation of meiotic proteins and affect gametophyte development.