Abstract
BackgroundMMS21 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.ResultsHere, 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.ConclusionsThus, these results suggest that AtMMS21 mediated SUMOylation may stabilize the expression and accumulation of meiotic proteins and affect gametophyte development.
Highlights
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
An immunoblot of total pollen grain proteins by anti-AtSUMO1 demonstrated a difference in the SUMO conjugates in wild-type and mms21-1, as some SUMOylation conjugates were missing in mms211 pollen grains proteins (Figure 7). These results suggested that AtMMS21 is involved in the SUMOylation of Arabidopsis pollen grains proteins, and may regulate the gametophyte developmental process through the SUMOylation pathway
Our results demonstrated that SUMOylation level in mms21-1 pollen grains proteins is different from the wild-type (Figure 7), indicating that AtMMS21-mediated SUMOylation may participate in generative cell formation
Summary
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. The haploid gametophytes are derived from the haploid spores that are produced by diploid megasporocytes (female) and microsporocyte (male)parent cells [1]. The megasporocyte undergoes meiosis to produce a tetrad of four haploid spores. Microsporocytes undergo meiosis to form a tetrad of four haploid microspores. Each microspore undergoes two mitotic divisions to form the Meiosis is a specialized cellular division that is conserved among most eukaryotes. This process is indispensable for formation of viable offspring. It consists of two rounds of chromosome segregation after a single round of DNA replication, giving rise to four haploid daughter cells. Disruption of meiotic homologous recombination could result in chromosome anomalies, which could lead to mis-segregation and aneuploidy [8]
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