Light-Regulated Transcription Factors Control Vindoline Biosynthesis in Catharanthus

[Music] [Music] welcome to nptl online certification

course on pharmacognosy and metabolic engineering we'll now go to lecture 26 where I will discuss the regulatory

role of transcription factors in light induced vindoline biosynthesis what we have seen in the

last class about the late steps of indol alcol pathway particularly how vindoline is biosynthesized from

tabarin so now what we are going to see what is the intrinsic regulation which light plays by involving different

transcription factors so let us go to the board so it's only one model we will study in this class a recent model that

depicts the regulatory role so I just now go to the board first I will draw a simple diagram and then I will draw a

complex diagram so first one just to remind you the pathway that means the

from triamine and sanin strictosidine

is formed and from strictosidine stto and aglycon is formed and that

ultimate ly leads to either asalin or through the formation

of O atile stemar

denin I have not mentioned this compound so this will come in the subsequent class where we where we desect the

pathway from stto in to tabersonine so that leads to one root goes to

cathan and other root goes to tonin and then finally it forms

vindoline so the arrows to be arrows to be added

here is just a reminder this this broken arrow means multiple step

pathway and then and here what we have learned recently

that the enzyme responsible for conversion of taronin to vindoline R T6

H then uh 16

omt then D3 3 O

then t3r then

nmt then d4h and then

d where what we are going to see

that D6 H D3 o t3r T4 h d a

t these will be these are influenced by by light

so what happens that light light and we will have to put

two transcription c r p i

f one and another one is c r g a t a

1 for so what I am showing here is basically

light induced uh tarpo indol alkaloid biosynthesis in catharanthus Rosas is

regulated by light so in other word what we can also write

that light regulated Vin

biosynthesis in cus so

crp1 phytochrome interacting Factor 1 so this basically suppresses

CR GA 1 so that is another transcription

Factor so pf1 suppresses CR G1 but it is

degraded by light and thus releasing CR G CR

G1 to activate the vindoline pathway so that means in the

dark crp1 basically suppress the positive regulator CR

gata1 and that leads to no vindoline formation in the dark okay but when light comes then that basically

suppresses CR P1 that is why you should we're showing here an arrow and that what happens as a result

of that crga ta1 is active which plays important role in vindoline

biosynthesis and also uh CR pif1 can also directly suppress

vindoline biosynthesis as well so this is in brief how vindoline biosynthesis is

regulated now in the next slide we are going to see in detail so

uh I have to draw a box so or not box we put a middle Arrow so the left side is under the dark

condition where okay this represents

the genes for CR GA A1 and this represents

the Gen for T6 H2

and d8 what happens CR

pf1 so crp1 we will put with the this is here

P 1 so this is binding

here this is binding here and maybe with the involvement

of another yet uncharacterized transcription

Factor so what it does it basically this actually this is the

transcription of these genes and this is the transcription of these

genes so it basically

blocks the transcription of these genes but when these genes activity are

blocked the basal activity is still maintained so the basal activity is

still maintained and that

probably by the help of this transcription

Factor next we what we see

t16 H to d a t

Okay transcription well see

M here but what we see here that there's another one that

is this is basically CR ga1 which also binds

here but on the next paragraph I will I will let me finish the drawing and then we'll

try to explain the next one for

so then what we see

the thearon in content for

that's there in and this

is Vin and what we put we

put 1 2 3 4 5 6 7 so

d a t d4h

nmt t3r t3o then 16

omt then T6 H2 so

here okay let me finish the drawing and then I'll try to

explain so here this side under light condition use the same

shape okay this is CR g a t A1 so

that unknown transcription factors binds and this this leads to

transcription and what happens here there's a light so under red light

condition CRP F1 is

getting degraded okay and now what we

see strong activation of of

CR GA ta1 and

then this leads to binding

of c g da1 here and that leads to transcription of gen

for t 16 H2 P3 o P3

r d4h d a t that

subsequently needs to t a v e r s o n i n

e but very strong flow for

vindin okay now one I will Mark here which are influenced by the

Light so this I can mark with rent so the diagram is

complete now I will try to explain

this so this is basically a model which depicting the regulatory

rules of the CR pf1 and CR gata1 module in light induced vindoline

biosynthesis so in the left side the there is a you see there is a bottom okay let me use

the laser pointer in the left side that mean this side what we see that crpf 1 is likely to accumulate in the dark

because this is the dark and it replaces the expression of CR

G1 so it replaces the expression as well as D16 H2 and d8 by binding to their promoter so it is

basically binding to their promoter site thus not allowing the RNA polymer to bind for starting the

transcription repression of this CR gataa actually this results also in the down regulation of the vindoline pathway

okay so when this is pressed so the vindoline pathway is down regulated and therefore we see that more tabarin is

accumulated but vindoline is less so this actually the repression of this

crg2 leads to basically the uh what it happens down regulation of the vindoline pathway gen like D16 H2

d8 so because it is binding it is not allowing the activity of this

uh also T30 t uh 3r d4h and D leading to limited vindoline production and increased

terson in accumulation but one unknown transcription factors which is denoted

with this florescent toolo that mediates the low or Basel expression of crg1

despite the uh CRP if1 reparation

so that means some basal level of CR g21 is expressed and that is why this is uh producing some amount but it is

mostly the tabon in that is why I put it in big circle now go to the right side where the crpf 1 is basically Al

degraded upon exposure of this catharanthus Rosia seedlings to light and which is mediated by a red light

sense phytochrome so here the phytochrome plays an important role in this crp1 degradation so as a result of

that there will be dation that means activation of crga and there this unknown transcriptor

factor May plays a positive role uh so this repression of crga this results in the activation of the

vindoline pathway so that means that CR G binds properly and all the MRNA for the subsequent genes will be

transcribed and uh what happens as a result of that vindoline accumulates the seven genes involved in

the conversion of Tavon into vindoline are basically listed here and uh where

with Gen which are responsive to red light I actually I put the red color underline that is 316

hydroxy uh t3o oxidase T3 reductase D4 D these are basically uh the genes which are

responsible to light induction so that is why the tonin content is now less and you see that more vindoline formation so

this is basically Ally how the light plays a regulatory role in conversion of tabon into vindoline and this beautiful

paper has been published by a group from Kentucky so I must write

the reference so this is uh published in plan physiology the

first author is Le at all and this uh this was published in

2019 in the highly respected Journal plan physiology volume

180 page number 1336 to 1350 and Indian senior post is involved in this work who is personally known to

me so with this Personal Touch I will end this course here thank you very much