In drosophila, the somatic cells of the hub are able to regulate stem cell proliferation by secreting the paracrine factor Unpaired onto the cells attached to them. Unpaired activates the JAK-STAT pathway in the adjacent germ stem cells to specify their self-renewal. Those cells that are distant from the paracrine factor cannot receive this signal, they begin their differentiation into the sperm cell lineage. This means hub cells act as

#Question id: 10369

#Unit 6. System Physiology – Plant

Which type of the nitrogen-fixing bacteria are thought to maintain a low oxygen concentration (microaerobic conditions) through their high levels of respiration

#Question id: 10370

#Unit 6. System Physiology – Plant

Rhizobial genes that participate in nodule formation are called nodulation (nod) genes. Only one of the nod genes, the regulatory and constitutively expressed and regulates the transcription of the other nod genes;

#Question id: 10371

#Unit 6. System Physiology – Plant

There are three essential nod gene for every bacterial species that is−NodA, NodB and NodC, that are required for synthesizing this basic structure such as;

a) NodA is an N-acyltransferase that catalyzes the addition of a fatty acyl chain

b) NodB is a chitin-oligosaccharide synthase that links the acetyl group of the terminal nonreducing sugar

c) NodC is a chitin-oligosaccharide synthase that links N-acetyl-D-glucosamine monomers

d) NodB is a chitin-oligosaccharide deacetylase that removes the acetyl group from the terminal nonreducing sugar

e) NodC is a chitin-oligosaccharide deacetylase that removes links N-acetyl-D-glucosamine monomers

Which of the following statements about NOD Factor is incorrect?

#Question id: 10372

#Unit 6. System Physiology – Plant

Nod genes, which NodD activates, code for nodulation proteins, most of which are involved in the biosynthesis of Nod factors such as;

 a) Nod factors are lipochitin oligosaccharide signal molecules

 b) Nod factor shave a chitin β-1→ 4-linked N-acetyl-D-glucosamine backbone

 c) These N-acetyl-D-glucosamine backbone varying in length from three to six sugar units

 d) A fatty acid chain on the C-2 position of the nonreducing sugar determine the length and degree of saturation of the fatty acyl chain by NodL

 Which of the following is incorrect?

#Question id: 10373

#Unit 6. System Physiology – Plant

The nodulation (nod) genes are classified as common nod genes or host specific nod genes. Some statements related to such classification are given below;

a) nod A is a common nod gene and nod Q is a host specific gene

b) nod B is a common nod gene and nod C is a host specific gene

c) nod C is a common nod gene and nod H is a host specific gene

d) nod H is a common nod gene and nod P is a host specific gene

Choose the correct answer from the above statements:

#Question id: 10374

#Unit 6. System Physiology – Plant

The stages in the formation of the symbiotic relationship between the nitrogen-fixing bacteria and their host, Arrange the given statements of symbiotic association in a stepwise manner;

 a) Migration of the bacteria toward the roots of the host plant by a chemotactic response mediated by chemical attractants

b) NodD with the flavonoids bind with the Promoter region of  highly conserved the nod box

c) These attractants activate the rhizobial NodD protein,

d) The chemical attractants especially (iso)flavonoids and betaines, secreted by the roots

e) Binding of the activated NodD to the nod box induces transcription of the other nod genes

 Which of the following from the above statements are correct arrangement of symbiosis?