Genetic Transformation of Plants: Introduction and Recent Advances

 

Dr. Shoaib Ahmad

University School of Pharmaceutical Sciences, Rayat-Bahra University, Mohali 140104 India

ABSTRACT:

Gram-negative soil bacteria belonging to the Genus Agrobacterium are used for genetic transformation of a variety of plants including medicinal plants. Typically, A. tumefaciens and A. rhizogenes are used in the induction of crown gall and hairy roots respectively. These transformed cultures can be used for generating better plants with increased adoption to  saline soils, drought, pests and pesticides. These cultures can also be used for exploiting secondary metabolism in plants and to manipulate the yield of phytoconstitutents. Genetic transformation of the economic and medicinal plants using Agrobacterium is promising tool in the plant biotechnology. The present article attempts to summarise the important advancements in the use of Agrobacterium for genetic manipulation.

 

 

 

INTRODUCTION:

Agrobacterium is a Gram-negative soil bacterium. Genetic transformation of the medicinal plants using Agrobacterium is an important tool in the plant biotechnology. A. tumefaciens and A. rhizogenes are commonly used in the genetic manipulation of the important medicinal, aromatic and economically important members of the plant kingdom. Crown gall and hairy roots are induced by use of A. tumefaciens and A. rhizogenes respectively. These transformed cultures have been explored for the purpose of metabolite engineering. The present article is an attempt to present the important advancements in the studies involving use of Agrobacterium for genetic manipulation.

 

Regeneration of Medicinal Plants:

Young stem segments from Lycium barbarum L. stem explants treated with Agrobacterium tumefaciens C58cl were utilized to produce regenerated plants¹. The stem explants of Morinda officinalis were co-cultivated with A. tumefaciens (strain EHA101), and later, used for plant regeneration². Agrobacterium-based transformation of Nicotiana africana Merxm. root explants have been used to produce kanamycin-resistant plants³. Leaf explants of Nicotiana tabacum and N. benthamiana co-cultured with A. tumefaciens GV3101 displayed active shoot regeneration property in cuture media without any plant hormones⁴. A. tumefaciens (EHA105) co-cultivated embryonic explants of Ricinus communis L. resulted in production of transgenic castor⁵. Eastern white pine (Pinus strobus L.) has been transformed using A. tumefaciens (strain GV3850)⁶. Embryogenic tissue of Norway spruce (Picea abies) was genetic transformed using A. tumefaciens to incorporate Cry3A gene of Bt⁷. Tomato (Solanum lycopersicum L.) was genetically manipulated with A. tumefaciens (strain EHA105)⁸.

 

Production of Secondary Metabolites:

Bacopa monnieri has been transformed with Agrobacterium rhizogenes strains LBA 9402. The transformed roots had higher content of phytoconstituents (bacopasaponin D, bacopasaponin F, bacopaside II and bacopaside V) than the normal roots⁹.  A. rhizogenes A4-mediated transformation of Catharanthus roseus led to hairy roots containing higher amounts of catharanthine. Catharanthine on reaction with vindoline forms anticancer drug vinblastine¹⁰. Transgenic "hairy" roots and plants of Cichorium intybus L. have been produced Agrobacterium species¹¹.

 

Improvement of Wheat:

Immature embryos of tetraploid Triticum turgidum L. var. durum were transformed using A. tumefaciens¹². Mature embryos of Triticum species (T. aestivum and T. durum) were transformed with A. tumefaciens LBA4404 strain¹³. T. aestivum L. and T. turgidum L. have been transformed using of A. tumefaciens¹⁴.

 

Improvement of Sorghum:

Sorghum bicolor (L.) Moench has been subjected to genetic manipulation using Agrobacterium and stable plants were successfully produced¹⁵. Bacillus thuringiensis (Bt) cry1Ab gene was incorporated into Sorghum (S. bicolor L.) using A. tumefaciens. The resultant plants have resistance to pink rice borer¹⁶.

 

Transformation of Commercial Crops

A. tumefaciens (strains EHA105, C58C1, and KYRT1) were used to produce recalcitrant Lens culinaris Medik¹⁷. Pineapple (Ananas comosus L., Merr.) leaf bases were treated with Agrobacterium  suspension. This system was used for growing pineapple plants¹⁸. Soybean was transformed using Agrobacterium species for establishing an efficient genetic transformation system for three Chinese genotypes (namely: Yuechun 04-5, Yuechun 03-3, and Tianlong 1)¹⁹.

 

Transformation of Fungal Species:

Conidia of Beauveria bassiana have been subjected to A. tumefaciens-mediated transformation which led to hygromycin resistant transformants²⁰. Fungus Penicillium digitatum has been subjected to transformation with A. tumefaciens.

 

Miscellaneous Cases of Genetic Manipulation:

Lycopersicon peruvianum var. dentatum has been successfully transformed with pG11 plasmid²². A. tumefaciens (EHA105) has been used for genetic transformation of Euonymus alatus hypocotyl explants for producing transgenic shoots²³. Agrobacterium tumefaciens has been used for genetic transformation of Ramonda myconi (L.) Rchb. and to produce plants free of morphological abnormalities²⁴. Platanus acerifolia Willd. has also been successfully subjected to genetic engineering using A. tumefaciens²⁵. Pogostemon cablin (Blanco) Benth. leaf explants were subjected to genetic transformation with Agrobacterium species and transformed plants were produced²⁶. Agrobacterium-mediated genetic transformation of Boehmeria nivea (L.) Gaud leaf midribs  led to production of transgenic plants²⁷. AgarTrap-mediated genetic transformation of Marchantia polymorpha L. has been reported²⁸.

 

CONCLUSIONS:

Genetic transformation of the economic and medicinal plants using Agrobacterium is promising tool in the plant biotechnology. These transformed cultures have potential for raising better plants which can withstand the adversaries such as calcinated soils, saline conditions, drought, pests and pesticides. These cultures can also be used for secondary metabolite engineering.

 

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Received on 06.03.2017          Modified on 18.03.2017

Accepted on 28.04.2017      ©AandV Publications All right reserved