A genome-wide association study identifies a transporter for zinc uploading to maize kernels.

The Zn content in cereal seeds is an important trait for crop production as well as for human health. However, little is known about how Zn is loaded to plant seeds. Here, through a genome-wide association study (GWAS), we identify the Zn-NA (nicotianamine) transporter gene ZmYSL2 that is responsible for loading Zn to maize kernels. High promoter sequence variation in ZmYSL2 most likely drives the natural variation in Zn concentrations in maize kernels. ZmYSL2 is specifically localized on the plasma membrane facing the maternal tissue of the basal endosperm transfer cell layer (BETL) and functions in loading Zn-NA into the BETL. Overexpression of ZmYSL2 increases the Zn concentration in the kernels by 31.6%, which achieves the goal of Zn biofortification of maize. These findings resolve the mystery underlying the loading of Zn into plant seeds, providing an efficient strategy for breeding or engineering maize varieties with enriched Zn nutrition.

Sec24C mediates a Golgi-independent trafficking pathway that is required for tonoplast localisation of ABCC1 and ABCC2.

Protein sorting is an essential biological process in all organisms. Trafficking membrane proteins generally relies on the sorting machinery of the Golgi apparatus. However, many proteins have been found to be delivered to target locations via Golgi-independent pathways, but the mechanisms underlying this delivery system remain unknown. Here, we report that Sec24C mediates the direct secretory trafficking of the phytochelatin transporters ABCC1 and ABCC2 from the endoplasmic reticulum (ER) to prevacuolar compartments (PVCs) in Arabidopsis thaliana. Genetic analysis showed that the sec24c mutants are hypersensitive to cadmium (Cd) and arsenic (As) treatments due to mislocalisation of ABCC1 and ABCC2, which results in defects in the vacuole compartmentalisation of the toxic metals. Furthermore, we found that Sec24C recognises ABCC1 and ABCC2 through direct interactions to mediate their exit from the ER to PVCs, which is independent of brefeldin A-sensitive post-Golgi trafficking pathway. These findings expand our understanding of Golgi-independent trafficking, which also provide key insights regarding the mechanism of tonoplast protein sorting and open a new perspective on the function of Sec24 proteins.

NPF transporters in synaptic-like vesicles control delivery of iron and copper to seeds.

Accumulation of iron in seeds is essential for both plant reproduction and human nutrition. Transport of iron to seeds requires the chelator nicotianamine (NA) to prevent its precipitation in the plant vascular tissues. However, how NA is transported to the apoplast for forming metal-NA complexes remains unknown. Here, we report that two members of the nitrate/peptide transporter family, NAET1 and NAET2, function as NA transporters required for translocation of both iron and copper to seeds. We show that NAET1 and NAET2 are predominantly expressed in the shoot and root vascular tissues and mediate secretion of NA out of the cells in resembling the release of neurotransmitters from animal synaptic vesicles. These findings reveal an unusual mechanism of transmembrane transport in plants and uncover a fundamental aspect of plant nutrition that has implications for improving food nutrition and human health.

[Current status and future prospects of anthropogenic particulate matter emissions in China].

The emission inventory of particulate matter (PM) in 2000 and 2005 were established based on the activity data and emission factors of power, industrial, residential and transportation sectors in China. Future emissions from 2010 to 2030 were projected under different scenarios of energy consumption and PM emission control policies. The emissions of TSP, PM10 and PM2.5 in 2005 were 29.98 Mt, 15.30 Mt and 9.79 Mt respectively, and the annual increasing rates were 3.4%, 4.7% and 5.4% during 2000 to 2005. By 2030, the emissions of TSP and PM2.5 would be 23.06 Mt and 10.59 Mt under reference scenario, of which industrial boilers are the largest contributor. With improvement of energy efficiency, the emissions of TSP and PM2.5 would be reduced by 15% and 16% respectively in 2030 compared with that under reference scenario. By intensifying the enforcement of legislation, 25% of TSP and 10% of PM2.5 can be further reduced in 2015. By tightening the emission standard and promoting high-efficiency dust collector after 2015, 21% of TSP and 19% of PM2.5 can be further reduced in 2030 and the emissions can become 13.81 Mt and 6.88 Mt separately. The control of particulate matter shall cover power, industrial and residential sectors. Actions shall include improving energy efficiency, enforcing legislation and tightening control policies.