Transgenic rice plants expressing synthetic cry2AX1 gene exhibits resistance to rice leaffolder (Cnaphalocrosis medinalis)

Abstract

Bacillus thuringiensis is a major source of insecticidal genes imparting insect resistance in transgenic plants. Level of expression of transgenes in transgenic plants is important to achieve desirable level of resistance against target insects. In order to achieve desirable level of expression, rice chloroplast transit peptide sequence was fused with synthetic cry2AX1 gene to target its protein in chloroplasts. Sixteen PCR positive lines of rice were generated by Agrobacterium mediated transformation using immature embryos. Southern blot hybridization analysis of T0 transgenic plants confirmed the integration of cry2AX1 gene in two to five locations of rice genome and ELISA demonstrated its expression. Concentration of Cry2AX1 in transgenic rice events ranged 5.0–120 ng/g of fresh leaf tissue. Insect bioassay of T0 transgenic rice plants against neonate larvae of rice leaffolder showed larval mortality ranging between 20 and 80 % in comparison to control plant. Stable inheritance and expression of cry2AX1 gene was demonstrated in T1 progenies through Southern and ELISA. In T1 progenies, the highest concentration of Cry2AX1 and mortality of rice leaffolder larvae were recorded as 150 ng/g of fresh leaf tissue and 80 %, respectively. The Cry2AX1 expression even at a very low concentration (120–150 ng/g) in transgenic rice plants was found effective against rice leaffolder larvae.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-015-0315-4) contains supplementary material, which is available to authorized users.

Codon usage bias

“…The cry genes of Bacillus thuringiensis and synthetic cry genes are transferred to crops for insect or pest resistance. A synthetic cry2AX1 gene (NCBI accession GQ332539.1) made with plant-preferred codons and expressed in rice and cotton showed significant protection against different types of lepidopteran insects [111][112][113]. However, designing of two kinds of codon optimised cry genes, one for monocot and another for dicot plants are also in vogue to improve the chances for getting events with desirable level of transgene expression.…”

Stacking of blast resistance orthologue genes in susceptible indica rice line improves resistance against Magnaporthe oryzae

“…Similar Southern blotting pattern among different transgenic rice lines was reported in an earlier study overexpressing Cry2ax1 gene to improve resistance against rice leaffolder disease. They further observed that the expression level of transgene varied among the lines with same banding pattern (Manikandan et al 2016). All the four stacked transgenic rice lines showed incompatible interaction with M. oryzae, but among them IET-23 was providing better resistance response than the rest.…”

Transient Expression of Plant-Codon-Optimized Cry2ab39 Gene by Agroinfiltration in N. Benthamiana

“…The challenge in development of Bt transgenic crops is the efficient and stable expression and translation of insecticidal genes and toxic protein in plant cells [21,22] . Initial attempts to introduce native Bt genes into transgenic plants resulted in extremely low levels of mRNAs and the corresponding proteins which were insufficient for protection of the crops from target insects [23] .…”

“…Codon optimization of bacterial genes based on codon usage of host plants was proved as one of the efficient ways to solve this issue. Synthetic Bt genes with modification in coding sequences were found to be expressed with the high efficiency in host plants and conferred insect resistance of the hosts [22,[24][25][26] .…”