Genetics of nitrogen-fixation, Biology

Assignment Help:

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.


Related Discussions:- Genetics of nitrogen-fixation

What are taenias, What are taenias? What are the diseases caused by them? ...

What are taenias? What are the diseases caused by them? Taenias, also called as tapeworms, are platyhelminth animals (flatworms). The major diseases caused by taenias are taeni

What is hypertension, Q. What is hypertension? The Hypertension is a di...

Q. What is hypertension? The Hypertension is a disease in which the arterial blood pressure, during systole or during diastole, is abnormally high. The Hypertension, or high

Spermatogenesis, Spermatogenesis: In the mature male functional sper...

Spermatogenesis: In the mature male functional sperm cells are produced within the seminiferous tubules of the testes. Around the periphery of the seminiferous tubules are l

How different is the gametogenesis in men and in women, Q. Concerning event...

Q. Concerning events during the periods of life how different is the gametogenesis in men and in women? The formation of spermatogonia in men takes place during the embryonic p

Biochemistry pathway of normal and cancer cell, Biochemistry pathway of nor...

Biochemistry pathway of normal and cancer cell Normal cells will separate within the presence of a chemical signal like as "growth factor" (GF). Other molecular signals

Explain renal insufficiency, Renal insufficiency  Antimicrobial drugs e...

Renal insufficiency  Antimicrobial drugs excreted through the urinary tract may be toxic for patients with renal insufficiency if they are given in usual therapeutic doses, bec

Heredity and variations, HEREDITY 1.         Like begets like i.e; ever...

HEREDITY 1.         Like begets like i.e; every living organism reproduces its own kind. Frog reproduce frogs, rats reproduce rats only. 2.         Heredity includes the cha

Explain functions of proteins, Explain Functions of proteins Functions ...

Explain Functions of proteins Functions of proteins are included herewith. These include: Source of energy: Constituent amino acids can be deaminated and metabolized to

Explain the term chemical score, Explain the term Chemical Score? Since...

Explain the term Chemical Score? Since egg proteins contain all essential amino acids in adequate amounts and possess the highest nutritive value among dietary proteins, Block

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd