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Polycomb group proteins are important repressors of numerous genes in higher eukaryotes. However, the mechanism by which Polycomb group proteins are recruited to specific genes is poorly understood. In Arabidopsis, LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), also known as TERMINAL FLOWER 2, was originally proposed as a subunit of polycomb repressive complex 1 (PRC1) that could bind the tri-methylated lysine 27 of histone H3 (H3K27me3) established by the PRC2. In this work, we show that LHP1 mainly functions with PRC2 to establish H3K27me3, but not with PRC1 to catalyze monoubiquitination at lysine 119 of histone H2A. Our results show that complexes of the transcription factors ASYMMETRIC LEAVES 1 (AS1) and AS2 could help to establish the H3K27me3 modification at the chromatin regions of Class-I KNOTTED1-like homeobox (KNOX) genes BREVIPEDICELLUS and KNAT2 via direct interactions with LHP1. Additionally, our transcriptome analysis indicated that there are probably more common target genes of AS1 and LHP1 besides Class-I KNOX genes during leaf development in Arabidopsis.

Autophagy is a highly regulated catabolic pathway that is potently induced by stressors including starvation and infection. An essential component of the autophagy pathway is an ATG16L1‐containing E3‐like enzyme, which is responsible for lipidating LC3B and driving autophagosome formation. ATG16L1 polymorphisms have been linked to the development of Crohn's disease (CD), and phosphorylation of CD‐associated ATG16L1 T300A (caATG16L1) has been hypothesized to contribute to cleavage and autophagy dysfunction. Here we show that ULK1 kinase directly phosphorylates ATG16L1 in response to infection and starvation. Phosphorylated ATG16L1 localizes to the site of internalized bacteria and stable cell lines harbouring a phospho‐dead mutant of ATG16L1 have impaired xenophagy, indicating a role for ATG16L1 phosphorylation in the promotion of anti‐bacterial autophagy. In contrast to wild‐type ATG16L1, ULK1‐mediated phosphorylation of caATG16L1 drives its destabilization in response to stress. In summary, our results show that ATG16L1 is a novel target of ULK1 kinase and that ULK1 signalling to ATG16L1 is a double‐edged sword, enhancing the function of the wild‐type ATG16L1, but promoting degradation of caATG16L1.

Meiosis, like mitosis, depends on the activity of the cyclin dependent kinase Cdk1 and its cyclin partners. Here, we examine the specific requirements for the three mitotic cyclins, A, B, and B3 in meiosis of Drosophila melanogaster. We find that all three cyclins contribute redundantly to nuclear envelope breakdown, though cyclin A appears to make the most important individual contribution. Cyclin A is also required for biorientation of homologs in meiosis I. Cyclin B3, as previously reported, is required for anaphase progression in meiosis I and in meiosis II. We find that it also plays a redundant role, with cyclin A, in preventing DNA replication during meiosis. Cyclin B is required for maintenance of the metaphase I arrest in mature oocytes, for spindle organization, and for timely progression through the second meiotic division. It is also essential for polar body formation at the completion of meiosis. With the exception of its redundant role in meiotic maturation, cyclin B appears to function independently of cyclins A and B3 through most of meiosis. We conclude that the three mitotic cyclin-Cdk complexes have distinct and overlapping functions in Drosophila female meiosis.

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