During an experiments mutating the conserved cysteine in the LOV1 domain of phot1 does not affect phototropic responsiveness (the seedlings bend toward blue light) whereas the equivalent mutation in LOV2 abolishes the response. What will be the conclusion has been drawn from this experiments?

a)  LOV1 domain is secondarily responsible (primarily responsible is LOV2 domain) for kinase activation and LOV1 is not is coupled with the protein region Jα-helix that’s why it does not affect phototropic responsiveness

b) These studies have demonstrated that LOV2 domain is primarily responsible for kinase activation in response to blue light

c) This is due in part to the position of LOV2 within the phototropin molecule, where it is coupled to a protein region known as the Jα-helix

d) The function of LOV2 domain is thought to play a role in receptor dimerization by accomplishing the kinase activation in response to blue light

Which of the correct conclusion drawn from the above experiment?

#Question id: 11824

#Unit 6. System Physiology – Plant

Only two of the ethylene receptors in Arabidopsis have intrinsic histidine kinase activity, these receptors are_______

#Question id: 11825

#Unit 6. System Physiology – Plant

Ethylene receptors are localized into the______

#Question id: 11826

#Unit 6. System Physiology – Plant

Some given statements about ethylene signalling pathways are listed;

a) Ethylene receptors are interact with two downstream signaling proteins, CTR1 (CONSTITUTIVE TRIPLE RESPONSE1) and EIN3 (ETHYLENE-INSENSITIVE3)

b) CTR1 is a soluble serine/threonine kinase that is associated with ethylene receptors, while EIN2 is an ER transmembrane protein with a cytosolic C-terminal domain that is a target for CTR1 kinase activity

c) EIN2 is required to stabilize transcription factors of the EIN3 (ETHYLENEINSENSITIVE3) family, which activate the transcription of ethylene-responsive genes

d) EIN3 is required to stabilize transcription factors of the EIN2 (ETHYLENEINSENSITIVE2) family, which activate the transcription of ethylene-responsive genes

Which of the following is the correct statements  of auxin signalling pathway ?

#Question id: 11827

#Unit 6. System Physiology – Plant

Which of the following enzyme is involved in the rate-limiting step in ethylene biosynthesis?

#Question id: 11828

#Unit 6. System Physiology – Plant

Given some enzymes of ethylene biosynthetic pathway and its character;

A) ACC synthase                                                               i) It is an unstable, cytosolic enzyme. Its level is regulated by environmental and internal factors, such as wounding, drought stress, flooding, and auxin

B) ACC oxidase                                                                  ii) It catalyzes the last step in ethylene biosynthesis, the conversion of ACC to ethylene

                                                                                                iii) Its activity can be the rate-limiting step in ethylene biosynthesis

                                                                                                iv) That is encoded by a multigene family that is differentially regulated

                                                                                                v) It is present in such low amounts in plant tissues and is very unstable and also difficult to purify the enzyme  for biochemical analysis

                                                                                                vi) These enzymes belong to the Fe2+/ascorbate oxidase superfamily

Find out the correct combination from the given enzymes and its character?

#Question id: 11829

#Unit 6. System Physiology – Plant

The certain cyclic olefin compounds, have been shown to block ethylene breakdown without inhibiting ethylene action?