In the frog (Xenopus laevis)

A gradient of the paracrine factor activin (a morphogen), causes concentration-dependent expression differences of two genes in unspecified cells.

TLS Online TPP Program

#Id: 7555

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7556

#Unit 6. System Physiology – Plant

Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

Induce cell division in callus cells in the presence of an auxin

Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

Delay senescence of leaves

Promote expansion of dicot cotyledons

TLS Online TPP Program

#Id: 7557

#Unit 6. System Physiology – Plant

Dihydrozeatin (DZ) and isopentenyl adenine (iP) also are commonly found in higher plants and bacteria.

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#Id: 7558

#Unit 6. System Physiology – Plant

Cytokinin biosynthesis, catalyzed by isopentenyl transferase (IPT), is the addition of the isopentenyl side chain from DMAPP (dimethylallyl diphosphate) to an adenosine moiety (ATP or ADP). iPRTP or iPRDP is converted to ZTP or ZDP respectively by cytochrome P450 monooxygenase (CYP735A) and eventually is converted to zeatin.

TLS Online TPP Program

#Id: 7559

#Unit 6. System Physiology – Plant

Many plant tissues contain the enzyme cytokinin oxidase, which cleaves the side chain from zeatin (both cis and trans), zeatin riboside, iP, and their N-glucosides, but not their O-glucoside derivatives

TLS Online TPP Program

#Id: 7560

#Unit 6. System Physiology – Plant

Cytokinin Primary site of synthesis -- root tips. High concentrations -- immature seeds and developing fruits