Specificity of strain and genotype in the susceptibility of pea to Agrobacterium tumefaciens

Development of a rapid and highly efficient Agrobacterium-mediated transformation system for pigeon pea [Cajanus cajan (L.) Millsp]

An efficient genetic transformation system is a prerequisite for studying gene functions, molecular breeding program, and introducing new traits. Agrobacterium tumefaciens-mediated genetic transformation is a widely preferred and accepted method for many plants, including pigeon pea. However, the efficiency of transformation of pigeon pea using the existing protocols is low and time-consuming. In the present study, we developed a rapid and highly efficient transformation system of pigeon pea, using embryonic axis-attached cotyledons as explants. We systematically investigated the influence of varying optical densities of Agrobacterium suspension, duration of incubation, and co-cultivation on the transformation efficiency. In our system, a transformation efficiency of approximately 83% was achieved using Agrobacterium cells at an optical density (OD₆₀₀) of 0.25, infection time of 15 min, and co-culturing with explants for 72 h in the light with 100µM acetosyringone. The entire procedure, starting from seed to establishment of transformed plants in soil, was achieved in 35-40 days. This is a rapid and highly efficient protocol for Agrobacterium-mediated transformation of pigeon pea, which could potentially be a useful reference, not only for the genetic improvement of pigeon pea but also for other recalcitrant leguminous plants.

Optimizing culture conditions for establishment of hairy root culture of Semecarpus anacardium L

Semecarpus anacardium L. is a tree species which produces secondary metabolites of medicinal importance. Roots of the plant have been traditionally used in folk medicines. Different strains of Agrobacterium rhizogenes (A4, ATCC15834 and LBA 9402) were used for induction of hairy roots in in vitro grown tissues of the plant. Hairy root initiation was observed after 25–30 days of infection. Optimum transformation frequency of 61% was achieved on leaf explants with ATCC15834 strain. Infection time of 30 min resulted in greater transformation frequency compared to 10 and 20 min, respectively. The hairy roots cultured in growth regulator-free semi-solid woody plant medium differentiated into callus. Whole shoots infected with ATCC 15834 were found to produce more transformants upon co-cultivation for 4 (65%) and 5 (67%) days. Induction of hairy roots in stem explants infected with ATCC 15834 was lower (52%) compared to leaves (62%) after 4 days of co-cultivation. In A4 and LBA9402 strains transformation efficiency was 49 ± 2.8% and 36 ± 5.7% in shoots after 4 days of co-cultivation. Transformation frequency was higher in ATCC15834 strain, irrespective of explants. The hairy roots of S. anacardium elongated slowly upon transfer to half-strength liquid medium. After 3–4 passages in liquid medium slender hairy roots started differentiating which were separated from the original explants. Visible growth of the roots was observed in hormone-free liquid medium after 2–3 months of culturing. Polymerase chain reaction with gene-specific primers from rol A, B and C genes confirms the positive transformation events.

Comparison of Soybean Transformation Efficiency and Plant Factors Affecting Transformation during the Agrobacterium Infection Process

The susceptibility of soybean genotype to Agrobacterium infection is a key factor for the high level of genetic transformation efficiency. The objective of this study is to evaluate the plant factors related to transformation in cotyledonary nodes during the Agrobacterium infection process. This study selected three genotypes (Williams 82, Shennong 9 and Bert) with high transformation efficiency, which presented better susceptibility to Agrobacterium infection, and three low transformation efficiency genotypes (General, Liaodou 16 and Kottman), which showed a relatively weak susceptibility. Gibberellin (GA) levels and soybean GA20ox2 and CYP707A2 transcripts of high-efficiency genotypes increased and were higher than those of low-efficiency genotypes; however, the opposite performance was shown in abscisic acid (ABA). Higher zeatin riboside (ZR) content and DNA quantity, and relatively higher expression of soybean IPT5, CYCD3 and CYCA3 were obtained in high-efficiency genotypes. High-efficiency genotypes had low methyl jasmonate (MeJA) content, polyphenol oxidase (PPO) and peroxidase (POD) activity, and relatively lower expression of soybean OPR3, PPO1 and PRX71. GA and ZR were positive plant factors for Agrobacterium-mediated soybean transformation by facilitating germination and growth, and increasing the number of cells in DNA synthesis cycle, respectively; MeJA, PPO, POD and ABA were negative plant factors by inducing defence reactions and repressing germination and growth, respectively.

Half-embryo cocultivation technique for estimating the susceptibility of pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) cultivars to Agrobacterium tumefaciens

Longitudinally sliced embryonic axes from pea and lentil mature seeds cocultivated with A. tumefaciens carrying a gus reporter gene in its T-DNA provided a convenient means to evaluate the efficiency of gene transfer to tissues in different cultivars and cocultivation conditions. Use of this technique demonstrated wide variation in susceptibility to Agrobacterium among several pea and lentil commercial genotypes.

A rapid and efficient regeneration system for pea (Pisum sativum), suitable for transformation

A method for plant regeneration via organogenesis in pea (Pisum sativum) using nodal thin cell layer segments has been developed.From 10 to 12 days old sterile pea seedlings, nodal expiants were excised from which leaves and axillary buds were removed. Shoot regeneration was consistently obtained from liquid cultures where the expiants were floated on the medium. Shoots could be harvested after two weeks and thereafter up to ten weeks and no important effect of the cultivar (Bodil, Puget, Rondo and Trille) used could be observed as far as shooting capacity was concerned.Rooting frequency of the regenerated shoots was cultivar dependent. Plantlets were obtained within 7 weeks after expiant excision. Agrobacterium tumefaciens carrying a disarmed Tiplasmid and a binary vector containing the ß-glucuronidase reporter gene, were used in cocultivation experiments on pea nodal expiants in order to obtain transgenic shoots.