In this connection, Dr. Imran Siddiqi and associates of the Centre for Cellular & Molecular Biology, Hyderabad have published a landmark paper in the 28 February 2008 issue of Nature.
Sustained productionHere they describe a key step towards the technology of sustained production of high yielding plants. This involves a genetic switching step that alters the sex life of the plant.
How many ways are there to produce a child? The answer depends on whom you ask. Many single cell organisms like bacteria have a ready, self-sufficient way of doing so.
They simply make a copy of their entire genetic content, the genome, and divide into two cells. In turn, each daughter divides into two, and the doubling goes on and on. Soon, from a single parent cell, millions and billons of cells are produced. This is a time-tested process called mitosis and has been going on for billions of years.
Since this mode of reproduction is from a single product, and as exact copies of it (well, almost exact), are made, the offspring are clones of the parent and the process is termed clonal expansion.
In multicellular organisms, cells not only divide as exact replicas, but also differentiate to produce other, different cell types. These differentiated cells, in turn, also clonally expand producing tissues and organs.
Clonal reproductionClonal reproduction is efficient but occasionally error-prone. When such copying error occurs, the information content in the DNA is compromised. Over time, organisms have evolved to contain proof-reading, editing and correcting mechanisms in their cells.
DNA-repair genes are contained endogenously within the cells. Yet, despite this, if the error stays and is copied into daughter cells, we have mutations.
When a mutation, per chance, offers a trait to the organism to withstand any environmental stress, it becomes beneficial and allows the mutant cells the advantage to survive better than the normal ones.
This is how drug-resistant bacteria evolve. On the other hand, mutations might occur which weaken a cell in some manner. If the genetic defect were to be carried over through generations, we then have a not so healthy family tree of this organism. It would thus be good to have other modes of gaining new and useful genes, and of reproduction.
If the same question is posed to mammals like us, the answer is: sex, where two parents, a female and a male, are needed to make children. Besides the 200-odd cell types that a female has, she prepares a special type called the egg cell or the ovum.
Genetic materialThis contains not all, but half of her genetic material. On his part, the male does likewise, packaging half his genetic material in a set of cells called the sperm.
The sperm cell meets the egg cell and fertilizes it to produce the embryo. The embryo develops in time and becomes the baby. The genes of the father and of the mother are thus passed on to the offspring.
Sexual reproduction of this kind has a great advantage over the clonal one. Brand new genes, and thus variety, are introduced. New traits and new possibilities arise.
And the female (and the male) has (in principle) the opportunity of choosing the partner to mate with, in order to produce healthy babies.
Gene mixing is the biological advantage of sex. But the cell biology involved is more complex than simple mitosis.
The splitting of the parent’s genetic content into making the germ cells (egg and sperm) first and then joining through fertilization involves two steps — meiosis and recombination.
Many plants too have taken this path. In the pistil of flowering plants are the egg cells (called ovules). The stamen is the male reproductive organ, which has anthers. Anther contains pollen, which are the male germ cells.
When pollen gets into the pistil and enters the ovule, fertilization happens. The result is the embryo, contained within seed. The surrounding cells of the ovule also divide to form the seed coat that nourishes the embryo within.
Desired qualitiesJust as we would (if we could) choose our mates with desired qualities and traits, we choose, while farming, to cross plants with desired qualities in their offspring.
These qualities are high yield, pest resistance, better fruits, more beautiful flowers and so on. In agriculture and major food crops, such well-chosen crosses lead to high yielding hybrids. The Green Revolution is the result of such an exercise.
But farmers face a problem. Once they have a good hybrid, they wish to keep its genes and propagate them by self-fertilizing the hybrid, so that the cultivars have superior yields than the parental inbred lines
ReshufflingSadly though, this hybrid vigour decreases with each generation of hybrid self crossing. The copies of the different genes in the hybrid separate from each other during germ cell production, and get reshuffled in each succeeding generation. As a result we need to cross the parental lines anew each time — not a satisfactory situation.
But there is way out. This comes from a peculiar property of many plants (and some animals such as insects and fish). Some plants such as dandelion, some berries and grasses side-step the meiosis process altogether and their seeds reproduce clonally, asexually.
The entire gene pool of the mother is passed on straight to the daughter seed. This curious, but exciting, property is referred to as apomixis, the first step of which is called apomeiosis (the apo-referring to the missing of a component).
While berries and grasses do this, major crop plants do not; they reproduce sexually. If only they could be made apomictic, we could retain hybrid vigour forever, since no reshuffling of genes as in sexual reproduction kind would occur.
If we understand the genetic and cell biological basis behind apomeiosis, we could perhaps send wheat, rice and corn along the apomixis path and produce high yielding hybrid seeds.
Important issueWhat are the genes controlling apomixis? It is this important issue that has been elegantly addressed and identified by Dr. Imran Siddiqi and co-workers, using the sexually reproducing plant Arabidopsis.
They show that alteration in the gene called DYAD leads to apomeiosis, sending the plant into the asexual mode. The DYAD gene normally regulates the organisation of chromosomes during meosis. Plants with mutation in DYAD, however, give rise to seeds that contain the full set of genes from the parent.
A single gene, whose function is known, can lead to a plant becoming apomictic, when its function is tampered with! This is truly a path-finding discovery and we should applaud the group for this breakthrough.
Imran, the soft-spoken and low-key aesthete, stoically adds: “(our) results provide impetus to search for additional genes which can be used in combination with DYAD to bring about apomixis in food crops, a major goal for agriculture biotechnology worldwide.” Tathastu!
Working in British Columbia in summer 2006, Cornell University researchers puzzled over the formation of granulite, which, unlike other rocks, forms under a wide range of depths but under a narrow range of temperatures.
In the continental crust, temperature was usually believed to increase almost linearly with depth — that is, the deeper the crust, the hotter the rock.
The scientists were in the business of backing into history — extrapolating what happened millions of years ago based on what they can observe now.
By studying what were once pockets of hot, melted rock 13 kilometres (about 8 miles) deep in the Earth’s crust 55 million years ago and calculating the period of cooling, the scientists attempted to find out how granulite is formed as the molten rock migrates upward through the crust.
The method usedUsing this method, the team of Cornell researchers has created a mathematical computer model of the formation of granulite.
They did so by looking at plutons, or pockets of hot, melted rock that were once as much as 13 kilometres below the Earth’s surface but are now exposed. (Plutons that rise to the surface and erupt can become volcanoes.)
The researchers found that the melted rock deep in the Earth is buoyant and will migrate upward through the crust to form a pluton.
Downward conductionHeat conducting downward from the hot pluton will, in turn, raise the temperature of the underlying rock to the pluton temperature.
They then realized that granulite can form at various depths but at similar temperatures.
The research is published in the March issue of the journal Nature by Gabriela V. Depine, a fourth-year graduate student in earth and atmospheric sciences (EAS); Christopher L. Andronicos, an EAS associate professor; and Jason Phipps-Morgan, professor of EAS.
Looking at the melting process is like looking at the process of the formation of continents, Andronicos explained, according to a Cornell University press release.
“If you look over geologic time, not all the rocks are the same age, and the reason for that is they got formed at different times,” he said.
Fundamental controls“So if you can get a handle on the temperature, which is what controls melting and metamorphism, then you have a better idea of some of the fundamental controls that lead to rock formation and, therefore, continents.”
The computer model, he said, hopefully will provide further insight into the energy balance of the Earth during crustal formation.
Exploitation and use of underground water using hand pumps and borewells always led to more salinisation as classically happened in Lakshadeep Islands when forage cultivation was encouraged using underground water.
Sea water intrusionThere was sea water intrusion and consequent salinisation. The rain water harvested during monsoon was collected in existing wells around the homestead and used to irrigate crops during summer.
Rain water conservation in sandy soils of coastal areas for irrigation was done in an indigenous way. Earthen pots with a hole at the bottom filled with water were placed near the roots of crops.
Many farmers in coastal zones of West Coast are still following this method with modifications like replacement of earthen pots with plastic pots. Pitcher system of irrigation is an innovative method to maximise rainwater efficiency.
Old practiceIt is an age-old practice to keep crops alive during periods of water shortage, according to Dr. K.V. Peter, Professor of Horticulture and Former Vice-Chancellor, Kerala Agricultural University. Earthen pots with one hole at the bottom are used. A cotton wig plugged into the bottom hole will release the water slowly based on the moisture in the soil.
Leaf mulching
In fact pitcher irrigation is as popular, or rather more popular than any other method of irrigation during summer or when water is scarce.
Leaf mulching along with pitcher irrigation further enhances water use efficiency, according to Dr. K.S. Purushan, Dean (fisheries), College of Fisheries, Panangad, Kochi. One of the advantages of using pitchers is their water saving capacity. But it has its limitations, as pitchers can be used only on a small-scale, while flood and sprinkler systems are for more extensive irrigation.
Energy is harvested from tiny movements
Piezoelectricity of zinc oxide powers the shirt
This is power-dressing in the real sense: nothing to do with shoulder pads or 1980s office dramas.
Zhong Lin Wang and his colleagues at the Georgia Institute of Technology in Atlanta have made a yarn out of nanofibres that produce charge when they are rubbed against one another. Materials woven from these yarns could be used for self-powering clothes, shoes or biological implants such as pacemakers.
Wang’s frustrationThe work is published in Nature. Wang became frustrated by the number of nanodevices being invented without the concurrent development of similarly sized powering technology.
“No matter how small these devices are, they still need battery power,” he says.
Wang decided that a nanoscale energy-producing device was needed, and turned to mechanical ways of producing that energy — from body motion, wind or even a heartbeat. “All this mechanical energy is wasted,” he says. Wang took standard synthetic Kevlar fibres and coated them with tetraethoxysilane, onto which they stuck a layer of zinc oxide.
Crystals of zinc oxide grew outwards, forming crystalline rods protruding from the fibres like the hairs on a brush.
Mechanical stressThe power comes from the zinc oxide, which is piezoelectric: When mechanical stress — such as bending, crushing or stretching — is applied to a piezoelectric material, it produces a voltage. Wang’s basic power-generating system involves two of these fibres, intertwined.
One of the two has its ‘brushes’ coated with a thin layer of gold. When the fibres rub against each other, the stiffer gold-coated brushes bend the non-coated brushes.
Charge build-upBecause of the piezoelectric effect, charge builds up on these bristles, and is gathered up by the gold-coated ones. “The metal on the brushes collects all this charge,” says Wang. Wires attached to the ends of the gold-coated and non-gold-coated fibres can carry the current to a device, such as a light bulb.
Cheap and simple“It is so cheap and simple,” says Wang: The brushes can be made easily in the lab, in beakers, at 80 degrees Celsius. “And it works.” When two strands were pulled and pushed against each other at a frequency of 80 times a minute, this produced 5-picoamp pulses of electricity.
Although this is a tiny amount, when a number of the fibres were woven into a yarn, the effect was much bigger. A yarn made from six fibres produced a current up to 50 times larger than that measured for the two-fibre nanogenerator.
Applications
As for applications, Wang imagines a ‘power shirt’ being made. “We want to make a yarn, and from a yarn make a fabric.” With this, he suggests applications for soldiers to power radio equipment, for example.
The material would have the advantage of harvesting energy — albeit a very small amount — from tiny movements. Even a heartbeat works to produce power, he says.
Because so far the biggest system made has comprised only six fibres, it is hard for Wang to estimate how much walking we are going to have to do to fire up our iPods, but the team estimates that a square metre of material could produce between 20 and 80 milliwatts of power from normal mechanical vibrations such as footsteps.
That is still far short of the amount of power required to illuminate a standard light bulb — around 60 watts — and a mobile phone, which needs about 1 to 3 watts.
Optimisation
Today, 5-watt solar panels can be used to help top up mobile phone batteries in the field. Wang is working to optimize the system.
He has patents on the fibres and a number of companies interested in developing the technology, he says.
“It’s certainly forward-looking,” says Joe Paradiso, director of the Responsive Environments Group at the Massachusetts Institute of Technology’s media lab.
He notes that it is not clear at this stage what kind of movement could generate the power needed for real applications, or whether these fibres could really work efficiently and reliably in something such as clothing or fabric. Wang believes they will, and expects a material to be produced within three years that is fully functional, flexible and wearable — although whether it will be fashionable remains to be seen.
| The aim is to detect and treat hypothyroidism and adrenal hyperplasia |
Hypothyroidism affects the brain, adrenal hyperplasia causes genital ambiguity in baby girls
The disorders are easy to detect and treatment is not expensive
While screening for these disorders, as well as others, is mandatory in the developed countries, the newborn screening programme, which is taken up on a pilot mode, will start only now.
“We have been brainstorming for the last 3-4 years,” said Dr. Vasantha Muthuswamy, Senior Deputy Director General, ICMR, New Delhi. “We are doing this on a research mode to gather data.”
The study is aimed at detecting and treating the disorders as soon as the baby is born.
“Ideally hypothyroidism should be detected from 48 hours after birth to 30 days. Delay of each day matters a lot,” noted Dr. Sujatha Jagadeesh, Consultant Geneticist at Mediscan, Chennai. Mediscan is the centre that will undertake the screening in Chennai.
While hypothyroidism affects brain development, adrenal hyperplasia leads to ambiguity in genital area in girl babies. The time of detection holds the key in reducing the amount of damage.
Later symptomsWhen detected and treated early, children will not show any symptoms. But any delay in detection will result in children showing up symptoms later in life. While many metabolic disorders can be screened, the programme has zeroed in on the two disorders as they are common in India.
These disorders are easy to detect and treat. And the treatments are not expensive. “We are screening for the disorders wherever intervention is possible. Otherwise it is ethically not right,” Dr. Muthuswamy said.
Preliminary dataThough the prevalence of these disorders in the country is not known, preliminary data based on ICMR’s multicentric newborn screening pegs the prevalence of hypothyroidism at 1 in 2,500 and 1 in 3,700 in the case of adrenal hyperplasia.
Mediscan in Chennai has screened 800 newborns at a government maternity hospital in Chennai and 1,600 at a corporate hospital in the city in the last eight months.
“We have not seen any positive cases. But the number is too small to draw any conclusions,” said Dr. Jagadeesh.
Newborn screeningThe newborn screening project undertaken on 23,000 children during 1999-2004 by the Hyderabad based Centre for DNA Fingerprinting and Diagnostics (CDFD) found the prevalence of the two disorders to be much higher.
“We found 1 in 1,800 newborns affected by hypothyroidism and 1 in 2,200 by adrenal hyperplasia,” said Dr. Radha Rema Devi, Genesticist at CDFD, Hyderabad. This screening was restricted to Hyderabad.
Rural communitiesCDFD has already started the newborn screening this January and has screened 800 babies so far. ‘Our programme is of little different. Dr. Devi said, “we plan to look at the rural communities in East Godavari District where consanguineous marriage is common.”
Mediscan, on the other hand, intends to screen a mixed population. It will target the Government Maternity Hospital in Chennai as well as private hospitals.
Whatever be the population studied, at least 95 per cent of newborns have to be screened to get any meaningful result.
According to Dr. Muthuswamy, ICMR plans to gradually include newborn screening for other diseases at a later date.
To run concurrent with the newborn screening programme will be the scrneening of 500 children who already have symptoms of the two disorders. This will be done at NIMHANS Bangalore. “This is to see our capability to detect these diseases. We may expand the number of diseases screened,” said Dr. Muthuswamy.
