Mercury contamination in food can pose serious health risks to consumers and coal-fired power plants have been identified as the major source of mercury emissions. To assess the current state of mercury pollution in food crops grown near coal-fired power plants, we measured the total mercury concentration in vegetables and grain crops collected from farms located near two coal-fired power plants. We found that 79% of vegetable samples and 67% of grain samples exceeded the PTWI’s food safety standards. The mercury concentrations of soil samples were negatively correlated with distances from the studied coal-fired power plants, and the mercury contents in lettuce, amaranth, water spinach, cowpea and rice samples were correlated with the mercury contents in soil samples, respectively. Also, the mercury concentrations in vegetable leaves were much higher than those in roots and the mercury content of vegetable leaves decreased significantly after water rinses. Our calculation suggests that probable weekly intake of mercury for local residents, assuming all of their vegetables and grains are from their own farmland, may exceed the toxicologically tolerable values allowed, and therefore long-term consumptions of these contaminated vegetables and grains may pose serious health risks.

Although cytokinins (CKs) regulate fruit development, no direct genetic evidence supports the role of endogenous CKs in pericarp growth or development or fruit size. Here, we report that the reduction in levels of endogenous active CKs via overexpression of the CK-inactivating enzyme gene AtCKX2 specifically in fruit tissues resulted in reduced pericarp thickness and smaller fruit size compared with wild-type control fruits. Pericarp thickness and single fruit weight in transgenic plants were significantly reduced. Analysis of paraffin sections showed that the reduced pericarp thickness was due largely to a decreased number of cells, and thus decreased cell division. Transcriptome profiling showed that the expression of cell division- and expansion-related genes was reduced in AtCKX2-overexpressing fruits. In addition, the expression of auxin-signaling and gibberellin-biosynthetic genes was repressed, whereas that of gibberellin-inactivating genes was enhanced, in AtCKX2-overexpressing fruits. These results demonstrate that endogenous CKs regulate pericarp cell division and subsequently fruit size. They also suggest that CKs interact with auxin and gibberellins in regulating tomato pericarp thickness and fruit size.

Hydrogen sulfide (H₂S) is an important gasotransmitter in mammals. Despite physiological changes induced by exogenous H₂S donor NaHS to plants, whether and how H₂S works as a true cellular signal in plants need to be examined. A self-developed specific fluorescent probe (WSP-1) was applied to track endogenous H₂S in tomato (Solanum lycopersicum) roots in site. Bioimaging combined with pharmacological and biochemical approaches were used to investigate the cross-talk among H₂S, nitric oxide (NO), and Ca²⁺ in regulating lateral root formation. Endogenous H₂S accumulation was clearly associated with primordium initiation and lateral root emergence. NO donor SNP stimulated the generation of endogenous H₂S and the expression of the gene coding for the enzyme responsible for endogenous H₂S synthesis. Scavenging H₂S or inhibiting H₂S synthesis partially blocked SNP-induced lateral root formation and the expression of lateral root-related genes. The stimulatory effect of SNP on Ca²⁺ accumulation and CaM1 (calmodulin 1) expression could be abolished by inhibiting H₂S synthesis. Ca²⁺ chelator or Ca²⁺ channel blocker attenuated NaHS-induced lateral root formation. Our study confirmed the role of H₂S as a cellular signal in plants being a mediator between NO and Ca²⁺ in regulating lateral root formation.

The biological function of RNA can be modulated by base modifications. Here, we unveiled the occurrence of N4-acetylation of cytidine in plant RNA, including mRNA, by employing LC-MS/MS and acRIP-seq. We identified 325 acetylated transcripts from the leaves of four-week-old Arabidopsis (Arabidopsis thaliana) plants and determined that two partially redundant N-ACETYLTRANSFERASEs FOR CYTIDINE IN RNA (ACYR1 and ACYR2), which are homologous to mammalian NAT10, are required for acetylating RNA in vivo. A double null-mutant was embryo lethal, while eliminating three of the four ACYR alleles led to defects in leaf development. These phenotypes could be traced back to the reduced acetylation and concomitant destabilization of the transcript of TOUGH, which is required for miRNA processing. These findings indicate that N4-acetylation of cytidine is a modulator of RNA function with a critical role in plant development and likely many other processes.