Pauline M. Doran
Department of Biotechnology, University of New South Wales,
Sydney, Australia
wrote:
I. INTRODUCTION
Hairy roots are formed by genetic transformation of plant cells using Agro-
bacterium rhizogenes. Integration into the plant genome of T-DNA from the
bacterial root-inducing (Ri) plasmid results in differentiation and growth of
hairy roots at the infection site. Hairy roots can be excised, cleared of excess
bacteria using antibiotics, and grown indefinitely in vitro by subculture of
root tips in liquid medium. Practical techniques for initiation, culture, genetic
manipulation, and molecular analysis of hairy roots are summarized in Ham-
ill and Lidgett (1). Hundreds of plant species have been successfully trans-
formed to hairy roots; lists of amenable species are provided in several pub-
lications(2-5).
For 15-20 years, hairy roots have been applied in a wide range of
fundamental studies of plant biochemistry, molecular biology, and physiol-
ogy, as well as for agricultural, horticultural, and large-scale tissue culture
purposes. Several recent reviews describe current and potential uses of hairy root cultures in research and industry (4–8). The aim of this chapter is to outline some of the emerging and rapidly developing areas of hairy root research and application. The properties and culture characteristics of hairy roots relevant to their scientific and commercial exploitation are summa- rized, and selected topics associated with organ coculture, foreign protein production, and the use of hairy roots in studies of phytoremediation and phytomining are reviewed.
II. PROPERTIES OF HAIRY ROOTS
There are several general features of hairy roots that confer significant tech- nical advantages to them compared with untransformed roots or dediffer- entiated plant cells. The attention given to hairy roots and their increasing adoption in scientific studies are due largely to properties such as
Genotype and phenotype stability
Autotrophy in plant hormones
Fast growth
High levels of secondary metabolites
It is important to realize, however, that not every hairy root culture displays
these characteristics. In addition, as well as advantages, many researchers have experienced problems with hairy root initiation and maintenance. Some of the common difficulties encountered are outlined in the following paragraphs.
A. Genotype and Phenotype Stability
Like most differentiated plant tissues, hairy roots exhibit a high degree of
chromosomal stability over prolonged culture periods (9). Stability has also
been demonstrated in terms of growth characteristics, DNA analysis, gene
expression, and secondary metabolite levels (10-13). Genotype and phe-
notype instability in hairy roots is therefore much less of a problem than in
callus and suspended plant cell cultures, where somaclonal variations in-
volving chromosome rearrangement and breakage, movement of transpos-
able elements, and gene amplification and depletion can occur with relatively high frequency (14).
The stability of hairy roots is an important advantage for both research
and large-scale industrial applications. Nevertheless, cytological instability
can sometimes occur, and there are several reports of variations in ploidy,
chromosome number, and chromosome structure in hairy root cultures (15 – 17). Very high rates of chromosome elimination were observed in hairy roots of Onobrychis viciaefolia during 12 months of culture (18). It is possible that the altered karyotypes sometimes observed in hairy roots could arise from the presence of endopolyploid nuclei in the host cell genome (17) or be the result of localized callusing due, for example, to tissue damage. Cal- lusing or loss of structural integrity is known to promote the development of polyploidy and aneuploidy in hairy root cultures (19). Minor structural
rearrangements of chromosomes in hairy roots were considered most prob-
ably to arise from terminal deletions of DNA (17). Notwithstanding these
observations, the frequency of chromosomal alteration in hairy roots is much
lower than in cultures of dedifferentiated plant cells.
And so on and on.
If someone are interested just write to me, and I will send whole book for you. (Plant BioTech)
Sincirely your Kuukulgur
Department of Biotechnology, University of New South Wales,
Sydney, Australia
wrote:
I. INTRODUCTION
Hairy roots are formed by genetic transformation of plant cells using Agro-
bacterium rhizogenes. Integration into the plant genome of T-DNA from the
bacterial root-inducing (Ri) plasmid results in differentiation and growth of
hairy roots at the infection site. Hairy roots can be excised, cleared of excess
bacteria using antibiotics, and grown indefinitely in vitro by subculture of
root tips in liquid medium. Practical techniques for initiation, culture, genetic
manipulation, and molecular analysis of hairy roots are summarized in Ham-
ill and Lidgett (1). Hundreds of plant species have been successfully trans-
formed to hairy roots; lists of amenable species are provided in several pub-
lications(2-5).
For 15-20 years, hairy roots have been applied in a wide range of
fundamental studies of plant biochemistry, molecular biology, and physiol-
ogy, as well as for agricultural, horticultural, and large-scale tissue culture
purposes. Several recent reviews describe current and potential uses of hairy root cultures in research and industry (4–8). The aim of this chapter is to outline some of the emerging and rapidly developing areas of hairy root research and application. The properties and culture characteristics of hairy roots relevant to their scientific and commercial exploitation are summa- rized, and selected topics associated with organ coculture, foreign protein production, and the use of hairy roots in studies of phytoremediation and phytomining are reviewed.
II. PROPERTIES OF HAIRY ROOTS
There are several general features of hairy roots that confer significant tech- nical advantages to them compared with untransformed roots or dediffer- entiated plant cells. The attention given to hairy roots and their increasing adoption in scientific studies are due largely to properties such as
Genotype and phenotype stability
Autotrophy in plant hormones
Fast growth
High levels of secondary metabolites
It is important to realize, however, that not every hairy root culture displays
these characteristics. In addition, as well as advantages, many researchers have experienced problems with hairy root initiation and maintenance. Some of the common difficulties encountered are outlined in the following paragraphs.
A. Genotype and Phenotype Stability
Like most differentiated plant tissues, hairy roots exhibit a high degree of
chromosomal stability over prolonged culture periods (9). Stability has also
been demonstrated in terms of growth characteristics, DNA analysis, gene
expression, and secondary metabolite levels (10-13). Genotype and phe-
notype instability in hairy roots is therefore much less of a problem than in
callus and suspended plant cell cultures, where somaclonal variations in-
volving chromosome rearrangement and breakage, movement of transpos-
able elements, and gene amplification and depletion can occur with relatively high frequency (14).
The stability of hairy roots is an important advantage for both research
and large-scale industrial applications. Nevertheless, cytological instability
can sometimes occur, and there are several reports of variations in ploidy,
chromosome number, and chromosome structure in hairy root cultures (15 – 17). Very high rates of chromosome elimination were observed in hairy roots of Onobrychis viciaefolia during 12 months of culture (18). It is possible that the altered karyotypes sometimes observed in hairy roots could arise from the presence of endopolyploid nuclei in the host cell genome (17) or be the result of localized callusing due, for example, to tissue damage. Cal- lusing or loss of structural integrity is known to promote the development of polyploidy and aneuploidy in hairy root cultures (19). Minor structural
rearrangements of chromosomes in hairy roots were considered most prob-
ably to arise from terminal deletions of DNA (17). Notwithstanding these
observations, the frequency of chromosomal alteration in hairy roots is much
lower than in cultures of dedifferentiated plant cells.
And so on and on.
If someone are interested just write to me, and I will send whole book for you. (Plant BioTech)
Sincirely your Kuukulgur
