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[SANET-MG] from the MADS house



February 23, 2005
“A view from the MADS  house”
       MADS-box genes are a large family of genes for protein transcription
factors  that read short DNA code ,the MADS-box, that  acts as a binding
domain for the MADS-box transcription regulator.  MADS-boxes and
transcription regulators are present in all eukaryotes from fungi to
plants and humans. The MADS-box and transcription factors regulate
pathways of development in multi-cellular organisms. The MADS-box
transcription factors bend DNA at the site of transcription initiation
to juxtapose transcription factors on adjacent sites (boxes)(1). In
plants the MADS-box gene families are conserved through the gymnosperms
, angiosperms, ferns and mosses.. They serve a wide range of functions
from floral  development  to root formation, but the range of effects is
not yet fully explored (2,3). The floral development pathways and time
of flowering  controls have common origin  (4). Flowering plants prefer
transcription from chromosomes of maternal rather than paternal origin
and even that epigenetic effect is expressed through  MADS-box  controls
(5).
       The discovery of the MADS-box  genes families has had an instant impact
 on agriculture and forestry. A wide array of inventions to control
flowering, seed production as well as other growth modifications has not
yet reached commercial farms and forests  but many modifications have
been reported and others have been patented.  A number of such
modifications will be described below. The main commercial transgenic
crops now available are modified for herbicide resistance or insect
resistance,  the MADS-box constructions  are modified with flowering
controls or flowering timing, even alterations in yield are
contemplated. Agronomy , horticulture and forestry will all be greatly
effected by the genetic modifications involving the MADS-box.
       Much of the initial work on the plant MADS-box transcription factors
was done using the  tiny mustard plant Arabidopsis. Recently a floral
transcription factor was found to control the agronomic traits seed
yield and seed mass (6,7).  Of course, such trait in Arabidopsis would
mainly please a few voles, but the trait can easily be manipulated in
grain crops such as maize, rice and wheat.  In rice , for example,
MADS-box genes have been identified which control flower  time, in rice
flower timing determines regional adaptability of rice varieties and
manipulating  that timing allows  greater use of regional varieties
(8,9). Genes determining rice floral morphology have been identified
allowing rice spikelet development to be manipulated (10).
       Vernalization  is the long winter  cold treatment  required for
flowering  in grain and some  oil crops.  Usually, the  crops requiring
vernalization  have spring planted cultivars that  do not require the
cold treatment so they can be planted in spring rather than autumn.
Nevertheless,  the winter requiring varieties have desirable traits that
 are not present in the spring varieties. In wheat vernalization  is
controlled by the MADS-box gene WAP1 (11). Unlocking vernalization
should  allow  quality wheat to be produced in warm climates. Bolting is
another aspect of cold temperature induced flowering. Exposing the
germinating seeds or plantlets to a range of low temperatures
accelerates flowering causing cabbage or lettuce to lose commercial
value. An anti-bolting  MADS-box gene has been identified in Chinese
cabbage (12). The stage is being set for  extensive  alterations in crop
geography.
       The MADS-box genes expressed during tomato seed and fruit development
have been identified (13).  Such findings may lead to commercial
applications.
       An anther specific MADS-box was identified in peas and found to be
expressed as well in a number of plant species.(14). The anther specific
transcription regulator can be manipulated to produce male sterile
varieties. Such varieties are used to produce high value hybrid seeds.
       A root nodule specific MADS-box gene was identified in alfalfa root
nodules(15).  Transferring  nitrogen fixing ability to non-legumes  has
been discussed for a number of years and the current development  may
spur developments in that area.
       The MADS-box gene DAL1 was identified as a mediator of juvenile to
adult transition in Norway spruce(16). Hastening floral development is
desirable in forest trees to accelerate breeding programs.
       The first , of  many, patents on MADS-box related functions have begun
to appear. United States Patent 6,828,478 by Yanofsky,Pelaz and Ditta
The  invention provides the surprising finding that ectopic expression
of certain MADS-box-containing gene products, such as SEP1, SEP2, SEP3
or AGL24, combined with the ectopic expression of AP1, CAL or LFY gene
products, result in modulated reproductive development. Thus, this
invention provides plants comprising such ectopically expressible gene
products as well as methods of modulating the timing of reproductive
development in plants.(17). The patent is a general one dealing with
reproductive development in plants. US patent 6,693,228  by Amasino
etal. Dealt with the flowering locus (FLC) to delay or advance flowering
(18). US patent 6,713,663 by Wiegel and Kardinsky deals with  FT protein
that modulates flowering in plants and dominant negative mutations of
that protein  (dominant negative mutations usually disrupt the function
of a wild type gene  by producing peptides that inactivate the wild type
product )(19). As in the previously described  patents the patent is a
general one dealing with  both angiosperms and gymnosperms.A Canadian
patent application  by Strauss et al deals with floral homeotic genes
for manipulation of flowering in poplar (20) That patent involves
ablation of reproductive cells  by using cell death toxins activated by
promoters for the flower specific transcription  factors or by
inhibiting the transcription factors using  genetic anti-sense or
dominant negative mutants. In  the patents described above  the genes
involved all originate from plants but selectable markers and synthetic
genes are used to modulate the plant genes.
       The discovery of MADS-box transcription regulators  has open doors to
modulation of  a wide array of properties valuable  for  agriculture.
The control of flowering  and seed production is only the first of many
areas including  nitrogen fixation, plant growth and disease resistance
where  the MADS-box family  can modulate genes  for agronomic and
horticultural traits. The potential  benefits from such manipulation
must be evaluated  based on the safety of the genetic modifications
themselves which may involve synthetic genes and  ablation toxins that
pose a threat to animals. Indeed ,the homology  between plant and animal
MADS-box genes should receive careful attention. The MADS-box has been
reshaping the  research on GM crops and it is here to stay. We must be
prepared to deal with  the emerging  GM crops  and to learn to deal with
the public relations  promoting  the crops and to  ensure that the crops
are safely evaluated before being  released to the environment.
References
1.      West,A. and Sharrocks,A. MADS-box transcription factors adopt
alternate mechanisms for bending DNA” 1999 Journal of Moleuclar Biology
 286,1311-23
2.      Ng,M. and Yanofsky,M. Function and evolution of the plant MADS-box
gene family 2001 nature reviews genetics  2,186-96
3.      DeBodt,S, Raes,J,VandePeer,Y. and Theissen,G. And then there were
many:MADS goes genomic 2003 Trends in Plant science 475-83
4.      Lawton-Rauh,A,Alvarez-Buylla,E. and Purugganan,M. Molecular evolution
of follower development 2000 Trends in Ecology and Evolution 15,144-9
5.      Autran,D,Huanca-Mamani,H. and Vielle-Calzada,J. Genome imprinting in
plants:the epigenetic version of the Oedipus complex 2005 Current
Opinion in Plant Biology 8,19-25
6.      Jofuku,K,Omidyar,P,Zorana,G. and Okamuro,J. Control of seed mass and
seed yield by the floral homeotic gene  APETALA2 2005  Proc. Natnl.
Acad.Sci. USA  102,3117-22
7.      Ohto,M,Fischer,R,Goldgerg,R,Nakamura,K. and Harada,J. Control of seed
mass by APETALA2 2005 Proc. Natl. Acad.Sci.USA  102,3123-8
8.      Doi,K,Izawa,T,Fuse,T,Yamanouchi,U. Kubo,T,Shimatan,Z,Yano,M. and
Yoshimura,A. Ehd1, a B-type response regulator in rice,confers short-day
promotion of flowering and controls FT-like gene expression
independently of Hd1 2004 Genes and Development 18,  926-36
9.      Lee,S,Kim,J,Han,J,Han,M. and An,G. Functional analyses of the
flowering time gene OsMADS50, the putative suppressor  of overexpression
of CO 1/agamous-like 20(SOC1/AGL20)ortholog in rice 2004 38,754-64
10.     Sentoku,N,Kato,H,Kitano,H. and Imai1,R. OsMADS22, an STMADS11-like
MADS-box gene of rice, is expressed in non-vegetative tissues and its
ectopic expression induces spikelet meristem indeterminacy 2005
Mo;ecular Genetics and Genomics in press
    doi 10.1007/s00438-004-1093-6
11.     Trevaskis,B,Bagnall,D,Ellis,M,Peacock,W. and Dennis,E. MADS box
genes control vernalization-induced flowering in cereals 2003 Proc.
Natnl.Acad.Sci.USA  100,13099-13104
12.     Lia,1,Z,Zhaoa,L,Cuib,C,Kaia,G,Zhanga,L,Sunc,X. and Tanga,K.
Molecular cloning and characterization of an anti-bolting related gene
(BrpFLC) from Brassica rapa ssp. Pekinensis  2005 Plant Science 168,407-13
13.     Busi,M, Bustamante,C, D’Angelo,C, Hidalgo-Cuevas,M,Boggio,S,
Valle,E.and Zabalet,E. MADS-box genes expressed during tomato seed and
fruit development 2003 Plant Molecular Biology 52,801-15
14.     Gomez,M,Beltran,J. and Canas,L. The pea END1 promoter drives anther
specific  gene expression in different plant species 2004 Plantaq 219,967-81
15.     Zucchero,J,Caspi,M. and Dunn,K.  ngl9: A Third MADS Box Gene
Expressed in Alfalfa Root Nodules 2001  Molecular Plant-Microbe
Interactions  14,1463-7
16.     Carlsbecker,A, Tandre‡,K,Johanson,U,Englund,M. and Engstro,P. The
MADS-box gene DAL1 is a potential mediator of the juvenile-to-adult
transition in Norway spruce (Picea abies) 2004 The Plant Journal  40,546-57
17.      Yanofsky,M,Pelaz,S. and Ditta,G. Combination of genes for producing
seed plants exhibiting modulated reproductive development  2004 United
States patent  6,828,478
18.     Amasino,R,Schomberg,F,Michaels,S,Sung,S. and Scortecci,K. Altering
of flowering in plants 2004 United States patent 6,693,228
19.     Weigel,D. and Kardailsky,I. Flowering locus T9FT) and genetically
modified plants having delayed flower development 2004  United States
patent  6,713,663
20.      Strauss,S,Rottman,W,Brunner,A. and Sheppard,L. Floral homeotic
genes for manipulation of flowering poplar trees and other plant species
Canadian patent application  2,319,853






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