Jun-Yu Chen

Rhizosphere microbes can protect plants from phytopathogens, but the molecular mechanisms are often poorly understood. Here, we report that a rhizosphere bacterium, Bacillus amyloliquefaciens strain TG1-2 displays antimicrobial activity against various phytopathogenic fungi and oomycetes, in a process that is mediated by the NatA acetyltransferase complex in the phytopathogenic fungus Verticillium dahliae. We show that acetylation of the molecular chaperone Hsp83 by NatA facilitates the formation of a co-chaperone complex Hsp83-Sti1-Hsp70 involved in protein quality control. Dysfunction of NatA or disruption of Hsp83 acetylation results in dissociation of the co-chaperon complex, increasing protein degradation and fungal apoptosis. Notably, TG1-2 and its major antimicrobial compound surfactin induce a reduction in Hsp83 acetylation, enhancing protein degradation and fungal apoptosis. Thus, our study provides insights into the mechanisms underlying the antimicrobial action of a rhizosphere strain against phytopathogenic fungi.

The phenomenon of multiple-grain spikelets is frequently observed in gramineous crops. In the case of dual-floret spikelets, the upper fertile floret develops normally to form a single grain, while the lower sterile floret undergoes abortion. Here we elucidate the role of Double-Grain 1 (DG1), a gene encoding a homeobox-domain-containing protein, in regulating the lower floret meristem activity and double-grain spikelet trait in sorghum. A 35.7-kb paracentric inversion in the DG1 promoter region leads to increased DG1 expression, probably by reducing repressive histone modifications. This increase in DG1 expression transforms the degenerated lower floret into a fertile one. The use of the superior DG1 allele results in an increase of approximately 40.7% to 46.1% in grain number per panicle and a 10.1% to 14.3% increase in overall grain yield. Our findings shed light on the sorghum double-grain spikelet characteristic, offering valuable insights for high-yield breeding designs in cereals.

Summary: Despite a much higher proportion of intragenic heterochromatin‐containing genes in crop genomes, the importance of intragenic heterochromatin in crop development remains unclear. Intragenic heterochromatin can be recognised by a protein complex, ASI1–AIPP1–EDM2 (AAE) complex, to regulate alternative polyadenylation. Here, we investigated the impact of rice ASI1 on global poly(A) site usage through poly(A) sequencing and ASI1‐dependent regulation on rice development. We found that OsASI1 is essential for rice pollen development and flowering. OsASI1 dysfunction has an important impact on global poly(A) site usage, which is closely related to heterochromatin marks. Intriguingly, OsASI1 interacts with the intronic heterochromatin of OsXRNL, a nuclear XRN family exonuclease gene involved in the processing of an miRNA precursor, to promote the processing of full‐length OsXRNL and regulate miRNA abundance. We found that OsASI1‐mediated regulation of pollen development partially depends on OsXRNL. Finally, we characterised the rice AAE complex and its involvement in alternative polyadenylation and pollen development. Our findings help to elucidate an epigenetic mechanism governing miRNA abundance and rice development, and provide a valuable resource for studying the epigenetic mechanisms of many important processes in crops.