Variation in the spatio-temporal expression of insecticidal genes in cotton

Abstract

Abstract:The most significant breakthrough in plant biotechnology is the development of the techniques to transform genes from unrelated sources into commercially important crop plants to develop resistance against targeted insect pests. The spatio-temporal expression of insecticidal genes in transgenic cotton varies with plant age, plant parts and environmental conditions. The understanding of this temporal and spatial variation in efficacy and the resulting mechanisms is essential for cotton protection and production. This review summarizes variations in the efficacy of introduced insecticidal genes in cotton crop. The factors contributing to the variability of endotoxins have also been highlighted. The reduction in Bt protein biosynthesis in late-season cotton tissues could be attributed to the overexpression of the Bt gene at earlier stages, which leads to gene regulation at post-transcription levels and consequently results in gene silencing at a later stage. Methylation of the promoter may also play a role in the declined expression of endotoxin proteins. In genetically modified crops several environmental factors have been reported to affect the expression of transgenes. Among environmental factors nitrogen metabolism, inhibition of synthesis, degradation, remobilization and high temperature are attributable to the quantitative reduction in Bt proteins. Applying plant growth regulators or protein enhancers such as Chaperone TM may improve Bt cotton efficacy through enhancing the synthesis of proteins. Also some agronomic practices such as nitrogen fertilization and timely irrigation favour the endotoxin expression. Thus, variations in the efficacy of insecticidal genes in transgenic cotton and the involved mechanisms need to be understood fully so as to plan rational resistance management strategies to retard the rate of resistance development and to control target pests effectively by enhancing the endotoxin expression through genetic or agronomic management.

Development of transgenic cotton lines harboring a pesticidal gene (cry1Ab)

“…The expression of transgenes in our lines varied in different generations. These results are in agreement with previous studies conducted by Wu et al (2002), Mahon et al (2002), Xia et al (2005), Adamczyk et al (2009 and Bakhsh et al (2011Bakhsh et al ( , 2012 who have reported inconsistency in insecticidal gene expression over the crop growth period and in various generations. However, investigation at molecular, genetic, as well as physiological levels should help in understanding the differential expression of transgenes and the quantitative changes in insecticidal proteins in insect resistant cotton plants.…”

Mendelian segregation pattern and expression studies of insecticidal gene (cry1Ac) in insect resistant cotton progeny

“…Mendelian inheritance of foreign genes in transgenic plants has been observed in alfalfa (Micallef et al, 1995), rice (Duan et al, 1996), maize (Fearing et al, 1997), cotton (Canming et al, 2000;Zhang et al, 2000;Xia et al, 2007;Zhang et al, 2007;Daud et al, 2009;Bakhsh, 2010) and cowpea (Ivo et al, 2008). However in some cases, incorporated gene exhibited distorted Mendelian segregation pattern (Spencer et al, 1992;Wan and Lemaux, 1994;Somers et al, 1994;Altman et al, 1996;Wu et al, 2002;Rashid et al, 2008;Bakhsh, 2010 Bakhsh et al (2010Bakhsh et al ( , 2011Bakhsh et al ( , 2012. There are many worth considering factors that can contribute variation in gene expression.…”

Expression of drought tolerance in transgenic cotton

“…Seasonal variations affect the transgene expression in different cotton lines. This variation for the transgene efficacy is correlated with the promoter activity 47,48 . The other factors reported for variation www.scienceasia.org in the level of gene expression, might be alteration in nucleotide sequence, gene integration point, copy number, cellular changes, and environmental factors 21,49 .…”