GPC Members Login
If you have any problems or have forgotten your login please contact [email protected]

A new regulator of vesicle trafficking in plants

A protein that transports the simple chemical choline plays a major role in vesicle trafficking, ion homeostasis, and growth and development in plants, according to two new studies published in the open-access journal PLOS Biology, by Dai-Yin Chao of the Shanghai Institutes for Biological Sciences, China, and Sheng Luan of the University of California, Berkeley, USA, and co-workers.

The protein, called choline transporter-like 1 (CTL1), had been previously identified as essential for formation of sieve plates, cell wall perforations that regulate passage of materials in plant phloem. But the mechanism of its function, and whether it played other roles in plants, was unknown. Chao and colleagues found CTL1 while screening for genes that control ion homeostasis in the model plant, Arabidopsis thaliana. They found that loss of CTL1 in the root led to ion disturbances in leaves, and deformations in plasmodesmata, a type of intercellular channel, in the root. CTL1 mutation also altered the distribution of ion transporters, which, combined with previous work localizing CTL1 to the trans-Golgi network, led the authors to investigate whether CTL1 played a direct role in vesicle trafficking. Sure enough, they showed that loss of CTL1 disrupted localization of multiple proteins, including an auxin transporter - auxin is the main growth hormone in plants.

Luan and colleagues began by mapping the distribution of CTL1 in Arabidopsis, and found that it was ubiquitous but was highest where auxin was highest: in the growing tips, in the vascular tissue, and in the "apical hook" that seedlings lead with as they push up through the soil. Intracellularly, they too found that CTL1 localized to the trans-Golgi network, and appeared to control trafficking to and from the plasma membrane; the authors observed that without CTL1, auxin transporters were misdirected, and the plant displayed the classic signs of auxin loss, including lack of cell elongation.

Chao also showed that excess choline inhibited endocytosis, mimicking the effects of CTL1 loss and suggesting that a critical CTL1 function is to sequester choline into endosomes. They suggest that keeping choline levels low outside endosomes promotes the activity of an enzyme, phospholipase D, that cleaves multiple lipids and, in so doing, has a direct effect on vesicle lipid composition and thus destination. In this model, loss of CTL1 raises choline, which inhibits the enzyme, altering vesicle lipids, and ultimately misdirecting the vesicles, which would account for the multiple effects of CTL1 mutation, including ion imbalances, plasmodesmata defects, and auxin mislocalization.

CTL1 is also found in animal cells, Chao noted, and thus the study concluded that "characterizing CTL1 as a new regulator of protein sorting may enable researchers to understand not only ion homeostasis in plants but vesicle trafficking in general."

Read the papers: A new vesicle trafficking regulator CTL1 plays a crucial role in ion homeostasis and Arabidopsis CTL1 regulates secretory trafficking of auxin transporters to control seedling growth.

Article source: PLOS.

Image credit: Sheng Luan


Forty years of data quantifies benefits of Bt corn adoption across multiple crops for the first time

University of Maryland researchers have pulled together forty years of data to quantify the effects of Bt field corn, a highly marketed and successful genetically engineered technology, in a novel and large-scale collaborative study. Other studies have demonstrated the benefits of Bt corn or cotton adoption on pest management for pests like the European corn borer or cotton bollworm in corn or cotton itself, but this is the first study to look at the effects on other offsite crops in North America. By tracking European corn borer populations, this study shows significant decreases in adult moth activity, recommended spraying regimens, and overall crop damage in vegetable crops such as sweet corn, peppers, and green beans. These benefits have never before been documented and showcase Bt crops as a powerful tool to reduce pest populations regionally thereby benefitting other crops in the agricultural landscape.

A lesson from Darwin on marine ecosystems

When British naturalist Charles Darwin traveled to the Galapagos Islands in 1835, he took notice of the giant kelp forests ringing the islands. He believed that if those forests were destroyed, a significant number of species would be lost. These underwater ecosystems, Darwin believed, could be even more important than forests on land.

Climate change risk for half of plant and animal species in biodiversity hotspots

Up to half of plant and animal species in the world's most naturally rich areas, such as the Amazon and the Galapagos, could face local extinction by the turn of the century due to climate change if carbon emissions continue to rise unchecked.