BULLETIN 1
PhilRice Study Pinpoints Low-GI Rice Varieties for Diabetics
ISAAA January 15, 2025

 

A team of scientists at the Philippine Rice Research Institute led by Dr. Marissa Romero identified rice varieties with low glycemic indexes, which can be beneficial to people with diabetes. Diabetes is the fourth leading cause of death in the Philippines.
The glycemic index is a value used for food based on how quickly it can cause blood sugar spikes. This means that food with higher GI is broken down into glucose more quickly, while foods with lower GI have a lesser impact on blood sugar levels. Excessive consumption of white rice, especially those with a GI of 70 or above, can contribute to the development of diabetes.
PhilRice's collaborator, the International Rice Research Institute, has previously reported a low-GI rice variety (NSIC Rc 182) using in vitro laboratory tests. Dr. Romero and her team used this variety as a reference to characterize the grain quality and pasting property indicators for low-GI rice. This led them to other low-GI rice varieties, namely NSIC Rc 472, PSB Rc 10, and Rc 514. Aside from their low-GI characteristic, these varieties are also high-yielding and resilient, thus favoring Filipino farmers, according to Dr. Romero.
The study won 3rd place Best Poster Award at the International Conference for Crop Science and Breeding.
Read more from PhilRice.

 

BULLETIN 2

Gene-silencing Spray to Fight Fusarium Head Blight in Cereal Crops

 

 

Researchers from the Swedish University of Agricultural Sciences (SLU) and James Hutton Institute have investigated how spray-induced gene silencing affects other microorganisms for the first time. This method is a step forward for a more sustainable farming system through an environmentally friendly alternative to chemical fungicides.
Fusarium head blight, caused by the fungus Fusarium graminearum, is a major threat to cereal crops, reducing yield and quality and posing a growing risk to global food security. Spray-induced gene silencing is a technique that could help manage the disease by targeting and silencing the genes the pathogen uses to infect the crop.
“We use a type of double-stranded RNA that regulates or blocks the pathogen's production of certain proteins that it needs to infect the plant,” said Ramesh Vetukuri, study leader and a Senior Lecturer at SLU. Their study showed that the double-stranded RNA successfully targeted the pathogen without affecting essential microbial communities. The findings of their study illustrate the potential of this method to fight Fusarium head blight without disrupting the balance in the ecosystem.
For more information, read the article from the Swedish University of Agricultural Sciences.
See: https://www.isaaa.org/kc/cropbiotechupdate/article/default.asp?ID=21169

 

SCIENTIFIC NEWS

The interaction of Serratia bacteria and harmonine in harlequin ladybird confers an interspecies competitive edge

Chaowei Zhang, Hang Zhou, Kang He, Yiqi Xiao, Mengyao Chen, Zhangqi Zuo, Runguo Shu, Yuhang Geng, Shuo Jin, Yang Mei, Bingbing He, and Fei Li
PNAS December 30, 2024; 122 (2) e2417873121; https://doi.org/10.1073/pnas.2417873121

 

  

Significance
Once prized for its use in biological pest control, the harlequin ladybird (Harmonia axyridis) has become an invasive pest in nonnative regions, outcompeting local ladybird species. Here, we found that the harlequin ladybird safely harbors Serratia harmoniae, a highly pathogenic bacterium that causes severe mortality in other ladybird species. The harlequin ladybird’s tolerance to the pathogen is attributed to the defense alkaloid harmonine. Silencing three key genes in the harmonine biosynthesis pathway—Spidey, Sca2, and Desat—reduced the production of harmonine, leading to increased bacterial levels and increased mortality. Penicillin treatment reversed this effect, reducing S. harmoniae content and increasing host survival. This symbiotic host–pathogen relationship confers an intraguild predation advantage to the harlequin ladybird.
Abstract
The harlequin ladybird, Harmonia axyridis, is a predatory beetle used globally to control pests such as aphids and scale insects. Originating from East Asia, this species has become highly invasive since its introduction in the late 19th century to Europe and North America, posing a threat to local biodiversity. Intraguild predation is hypothesized to drive the success of this invasive species, but the underlying mechanisms remain unknown. In this study, a feeding assay revealed that while harlequin ladybirds survive feeding on seven-spotted ladybird eggs, the reverse is not true. However, seven-spotted ladybirds that had fed on harlequin ladybird eggs were able to survive the feeding assay when treated with penicillin. Microbiome sequencing and whole genome analysis of harlequin ladybird eggs revealed a newly discovered pathogenic bacterium strain named Serratia harmoniae. The median lethal concentration (LC50) of S. harmoniae was found to be 2.1 × 105 times higher in the harlequin ladybird compared to the seven-spotted ladybird. The high tolerance observed in harlequin ladybirds was attributed to harmonine, specifically produced in the fat body of this species. Silencing three key genes in the harmonine biosynthesis pathway—Spidey, Sca2, and Desat—reduced the production of the compound, leading to increased S. harmoniae levels and higher mortality. Treating RNAi-altered individuals with penicillin reversed this effect, successfully reducing S. harmoniae presence and increasing insect survival. Taken together, these findings demonstrate that S. harmoniae, a newly identified pathogenic bacterium carried by harlequin ladybirds, interacts with harmonine to confer an interspecies competitive advantage over native ladybird species in nonnative regions.
See https://www.pnas.org/doi/10.1073/pnas.2417873121

 

  

Figure:
Mechanisms of harmonine protection against S. harmoniae. The C16 precursor is obtained through the hydrolysis of lipid droplets and subsequently enters the endoplasmic reticulum in the presence of Malonyl-CoA, contributing to fatty acid elongation and the formation of stearic acid. This is catalyzed by a HaDesat-mediated enzyme to form oleic acid, which undergoes a series of oxidative, dehydrating, and amination reactions, resulting in harmonine production. Harmonine is then released to extracellular spaces along with body fluids to resist S. harmoniae.