Thursday, 19 September 2019

Study Paves The Way For New Approach To Boost Rice Yield

Scientists at the National Institute of Plant Genome Research (NIPGR) have identified a gene that is involved in regulating the size of rice grain.

BY Sunderarajan Padmanabhan Published in India Science Wire

Dr. Jitendra K. Thakur and his research team at NIPGR, New Delhi
Rice productivity in India is low compared to other countries like China and Japan though it has the largest area under rice cultivation. Now scientists at the National Institute of Plant Genome Research (NIPGR) here have identified a gene that is involved in regulating the size of rice grain.

The new development represents a new approach towards developing rice varieties that produce bigger and consequently heavier grains.

The researchers had found in earlier studies that expression of a particular gene, OsMed15a, was higher at different stages of seed development. The observation led them to explore its role further. They scanned 509 different rice genotypes and found that the nucleotide sequences of the OsMed15a gene varied depending on size of grain. OsMed15a was also found to play major role in regulating the expression of three other genes - GW2, GW5 and DR11I- which determine grain size and weight.

“When we suppressed the expression of OsMed15a in transgenic plants using RNAi technology, the seeds became smaller and wider,” explained Dr. Jitendra K. Thakur, lead researcher, while speaking to India Science Wire. For further work, the group is collaborating with Ranchi-based Indian Institute of Agriculture Biotechnology so that grain size could be increased substantially through standard breeding methods.

“This study is important as it establishes OsMed15a as a connecting link between some of the different genes important for grain size/ weight trait in rice. In the next phase, using high throughput ‘omics’ tools, we would be delineating complete network of genes and proteins being connected through OsMed51a,” Dr. Thakur said.

He also noted that the size and shape ofrice grain is not only important for boosting yield but also contribute to the market value of rice. “Indians prefer long and slender rice grains. There are some small grain rice which are full of pleasant aroma. We are trying to introgress long grain allele of OsMed15a in these varieties so that the seeds become longer. We hope that in this way we would be able to produce location-specific long grain aromatic rice”, he added.

The research team included Dr. Swarup K. Parida, Nidhi Dwivedi, Sourobh Maji, Mohd Waseem, Pallabi Thakur and Vinay Kumar. The study results will be published in journal BBA - Gene Regulatory Mechanisms. This work was supported by grants from Science and Engineering Research Board (SERB) and Department of Biotechnology (DBT).

Tuesday, 17 September 2019

IISc Study Sheds Light On How A Midbrain Region Helps Us Pay Attention

Researchers at the Indian Institute of Science (IISc) have identified how a key midbrain region plays a vital role in attention in humans, using advanced imaging and modelling techniques.


(Devarajan Sridharan and Varsha Sreenivasan)

The human brain is regularly bombarded with information. It is through attention that it makes decisions efficiently: it processes relevant information and tunes out distractions. Understanding how attention works in the brain and how it controls behaviour can help scientists understand disorders such as Attention-Deficit Hyperactivity Disorder (ADHD), according to Devarajan Sridharan, Assistant Professor at IISc’s Centre for Neuroscience and his PhD student Varsha Sreenivasan, who recently published their findings in the  journal Proceedings of the National Academy of Sciences.

Attention is widely associated with the outermost layer of the brain tissue called the cerebral cortex, which is also linked to awareness, thoughts, memory, language, and consciousness. It is only recently that scientists began linking a midbrain region called the Superior Colliculus (SC) with attention.

“SC is an evolutionarily conserved midbrain structure that can be found in all vertebrates, including fish, lizards, birds and mammals. It is usually studied for its role in controlling eye movements,” explains Sreenivasan.

To demonstrate its role in attention, scientists had in recent years studied behaviour in monkeys during attention-demanding tasks. They observed that the monkeys were attentive when the SC was stimulated and distracted when this part of the brain was silenced.

But scientists were not sure how exactly SC promotes attention in humans: was it focusing on the target visual stimulus over several others for decisions (increased choice bias) or was it enhancing the visual clarity of the target stimulus (increased visual sensitivity)? Bias- or sensitivity-mediated attention plays out in situations that require rapid and selective decision making, for instance, at a traffic signal.

Consider this example: you are driving on a foggy morning and you stop at a signal. The signal appears green, but you are unsure. As you are in a hurry, your brain decides that it is green and you drive away. In this case, your choice bias towards the green signal is guiding your decision. In an alternate scenario, you see that the fog is lifting gently. You detect a flicker of the green light and you drive away. Here, your visual sensitivity towards the green signal increases, which then helps your decision-making process. While a few recent studies have made the case for SC’s role in controlling choice bias, others have leaned towards visual sensitivity.

To address this debate, in the current study, Sreenivasan and Sridharan conducted two sets of experiments in human participants, using non-invasive techniques. In one, they conducted a behaviour test on 22 participants, where they tracked changes in bias and sensitivity during attention-demanding tasks. In the second experiment, they studied the anatomy of SC in 82 participants, including the 22 tested earlier. Using an imaging technique called diffusion Magnetic Resonance Imaging (dMRI), and a 3D modelling technique called tractography, they tracked white matter fibres in the brain connecting the SC with other regions, including the cortex.

When they compared the results of the two experiments, they found that SC strongly connects with a part of the cerebral cortex called the parietal cortex, which has previously been associated with attention. They also show that the strength of SC-cortex connectivity can predict individuals’ bias, but not sensitivity.

“We also show that choice bias is stronger, on average, towards the right side of our visual field. Interestingly, SC connections in the cortex also mirror this asymmetry for bias, which further underscores the relationship between SC and bias,” explains Sridharan.

In the future, the team plans to study the activity of SC using a different imaging technique called functional MRI (fMRI) that can identify increased blood oxygen levels in areas of the brain that are activated during tasks. Sreenivasan adds, “Through fMRI, we will investigate if SC’s activity correlates with behavioural measures of sensitivity and bias. Our approach can also help understand if SC-cortex connection asymmetries are predictive of certain kinds of attention disorders such as ADHD.”

Journal Reference:
Subcortical connectivity correlates selectively with attention’s effects on spatial choice bias