Plant Physiology: Plant Signals and Signal Transduction
Channel: ScenseMe
Date: 2022-12-26

Delivered on: 07 NOVEMBER 2022

Overview Slides: ADVANCED CROP PHYSIOLOGY AGR4301 FALL- 2022
https://1drv.ms/b/s!ApP1hfaZ_IRqjfA5fgnoXCnrFnCuaA?e=gNptkN


As sessile  organisms, plants  constantly make adjustments
in response to their environment, either  to take advantage of favorable conditions or to survive unfavorable ones. To facili- tate  such adjustments, plants  have evolved sophisticated sensory systems to optimize water and nutrient usage; to monitor light
quantity, quality, and directionality; and to defend themselves from biotic and abiotic  threats. Charles  and Francis Darwin performed pioneering studies on signal transduction during  the bending growth of grass  coleoptiles in response to light. They observed that a unidirectional light source was perceived at the coleoptile tip, yet the bending response took place  farther  back along  the shoot tis- sue. This led the Darwins to conclude that there must be a mobile signal that transferred information from one  region of the coleoptile tissue  to another and elicited the bending response. The mobile signal was later identified as auxin, indole-3-acetic acid, the first plant hormone to be discovered.
In general, an environmental input that initiates  one  or more plant responses is referred to as a signal, and the physical com- ponent that biochemically responds to that signal is designated a receptor. Receptors are either  proteins or, in the case  of light recep- tors, pigments associated with proteins. Once receptors sense their specific signal, they must transduce the signal (i.e., convert it from one  form to another) in order to amplify the signal and trigger the cellular response. Receptors often  do this by modifying  the activity of other proteins or by employing intracellular signaling molecules called  second  messengers; these molecules then  alter cellular processes such as gene transcription. Hence, all signal transduction pathways typically involve the following chain of events:
Signal → receptor → signal transduction → response

In many cases  the initial response is the production of secondary signals, such as hormones, which are then  transported to the site of action  to evoke  the main physiological response. Many of the
specific events and intermediate steps involved in plant  signal trans- duction have now been identified, and these intermediates consti-
tute  the signal transduction pathways.


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