Genetics of nitrogen-fixation, Biology

Genetics of Nitrogen-fixation

The genetics of nitrogen-fixation is known in detail in Klebsiella pneumoniae. There are twenty genes required in organising the complete N2-fixing apparatus. Interestingly, it has been shown that if all the twenty genes of Klebsiella are transferred to E coli, a non-N2-fixer, the latter becomes a N2-fixer. Some nif genes code for the structural components of nitrogenase while two genes (nif L and nif A) are regulatory. The fast growing Rhizobia like R. leguminosarum are knouin to contain three kinds of genes for N2-fixation. They are

  1. nif-genes required for the formation of functional nitrogenase as in Klebsiella,
  2. Nod-genes required for the formation of nodules in root and
  3. Fix-genes required for the maintenance of N2-fixation by the nodule.

They control oxygen protection of nitrogenase as well as ATP and reductant supply. There are about 18 nod-genes known which are activated by the inducer - flavonoid (leutolin) present in the exudate of roots. They are supposed to be involved in controlling various stages of Rhizobium infection leading to the formation of nodule. The nif, the nod and the fix genes are located on a plasmid in the fast growing rhizobia and on the chromosome in slow growing rhizobia. Nod-genes are known to control the host-range of the bacterium and it should be genetically possible to increase its host range, thus enabling it to infect cereals and produce root nodules on them. Recently cultured tissues of rice and wheat have been successfully infected with Rhizobium although the association does not have the capability of fixing nitrogen. This achievement, however, is a step closer to Rhimbium-wheat or Rhizobium-rice N2-fixing system.

Posted Date: 1/17/2013 5:14:12 AM | Location : United States







Related Discussions:- Genetics of nitrogen-fixation, Assignment Help, Ask Question on Genetics of nitrogen-fixation, Get Answer, Expert's Help, Genetics of nitrogen-fixation Discussions

Write discussion on Genetics of nitrogen-fixation
Your posts are moderated
Related Questions
What is the water cycle? The water cycle represents the circulation and recycling of water in nature. Liquid water on the planet surface is heated by the sun and turns into

Define Factors Affect Management and Prognosis of Root Perforation Time Location of defect in relation of crestal bone Level of perforation Size Periodo

MULTIPLE ALLELES (i)         More than two alternative forms (alleles) of a gene in a population occupying the same locus on a chromosome or its homologue are known as multiple

Define Criteria for Assessment of Pyridoxine Status? Vitamin B 6 status is most appropriately evaluated by using a combination of indicators,  namely plasma PLP concentration,

What are the differences between blood retinal barrier and blood aqueous barrier? Blood Retinal Barrier: Blood retinal barrier is present in retina. In retina there are t

PURPOSES OF PATIENT's /CLIENT's RECORDS Following purposes are served by maintaining patient's/client's records: A means of communication.  A basis on which therap

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

GROWTH CURVE - Sigmoid curve or stretched 'S' shaped curve is obtained showing - a - lag phase                              b - log phase c - in flaxion p

Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualised within the human body. Radiologists use an array of imaging technolog

Amniocentesis is a way of prenatal testing in which the amniotic fluid is withdrawn from the uterus by the help of a needle. The fluid and the fetal cells it contains are analyzed