Cross Inhibition of MPK10 and WRKY10 Participating in the Growth of Endosperm in Arabidopsis thaliana.

The product of double fertilization produces seed, which contains three components: triploid endosperm, diploid embryo, and maternal seed coat. Amongst them, the endosperm plays a crucial role in coordinating seed growth. Mitogen-activated protein kinase (MAPK) cascades are conserved in eukaryotes and involved in signal transduction of plant development. MPK3, MPK6, and MPK10 form a small group of MPKs family in Arabidopsis thaliana. MPK3 and MPK6 are extensively studied and were found to be involved in diverse processes including plant reproduction. However, less is known about the function of MPK10. Here, we found WRKY10/MINI3, a member of HAIKU (IKU) pathway engaging in endosperm development, and MPK10 is high-specifically expressed in the early developmental endosperm but with opposite gradients. We further proved that MPK10 and WRKY10 cross-inhibit the expression of each other. The inhibition effect of MPK10 on gene expression of WRKY10 and the downstream targets is supported by the fact that MPK10 interacts with WRKY10 and suppresses the transcriptional activity of WRKY10. Constantly, mpk10 mutants produce big seeds while WRKY10/MINI3 positively regulate seed growth. Altogether, our data provides a model of WRKY10 and MPK10 regulating endosperm development with a unique cross inhibitory mechanism.

Transcriptome analysis of a taxol-producing endophytic fungus Cladosporium cladosporioides MD2.

The shortage of molecular information for taxol-producing fungi has greatly impeded the understanding of fungal taxol biosynthesis mechanism. In this study, the transcriptome of one taxol-producing endophytic fungus Cladosporium cladosporioides MD2 was sequenced for the first time. About 1.77 Gbp clean reads were generated and further assembled into 16,603 unigenes with an average length of 1110 bp. All of the unigenes were annotated against seven public databases to present the transcriptome characteristics of C. cladosporioides MD2. A total of 12,479 unigenes could be annotated with at least one database, and 1593 unigenes could be annotated in all queried databases. In total, 8425 and 3350 unigenes were categorized into 57 GO functional groups and 262 KEGG pathways, respectively, exhibiting the dominant GO terms and metabolic pathways in the C. cladosporioides MD2 transcriptome. One potential and partial taxol biosynthetic pathway was speculated including 9 unigenes related to terpenoid backbone biosynthesis and 40 unigenes involved in the biosynthetic steps from geranylgeranyl diphosphate to 10-deacetylbaccatin III. These results provided valuable information for the molecular mechanism research of taxol biosynthesis in C. cladosporioides MD2.