Use of 13C labeling to assess carbon partitioning in transgenic and nontransgenic (parental) rice and their rhizosphere soil microbial communities

Abstract

Photosynthetic assimilation of CO2 is a primary source of carbon in soil and root exudates and can influence the community dynamics of rhizosphere organisms. Thus, if carbon partitioning is affected in transgenic crops, rhizosphere microbial communities may also be affected. In this study, the temporal effects of gene transformation on carbon partitioning in rice and rhizosphere microbial communities were investigated under greenhouse conditions using the 13C pulse‐chase labeling method and phospholipid fatty acid (PLFA) analysis. The 13C contents in leaves of transgenic (Bt) and nontransgenic (Ck) rice were significantly different at the seedling, booting and heading stages. There were no detectable differences in 13C distribution in rice roots and rhizosphere microorganisms at any point during rice development. Although a significantly lower amount of Gram‐positive bacterial PLFAs and a higher amount of Gram‐negative bacterial PLFAs were observed in Bt rice rhizosphere as compared with Ck at all plant development stages, there were no significant differences in the amount of individual 13C‐PLFA between Bt and Ck rhizospheres at any growing stage. These findings indicate that the insertion of cry1Ab and marker genes into rice had no persistent or adverse effect on the photosynthate distribution in rice or the microbial community composition in its rhizosphere.

13C pulse‐labeling assessment of the community structure of active fungi in the rhizosphere of a genetically starch‐modified potato (Solanum tuberosum) cultivar and its parental isoline

“…The use of this marker as an indicator of fungal biomass is often debated, but, as we found a highly significant positive correlation between PLFA 18:2x6.9 and active fungal ITS copy number, we conclude that this marker is a useful indicator of fungal biomass in the rhizosphere, despite the presence of living roots (Frostegård et al, 2011). Earlier studies also showed that fungi quickly incorporate carbon from plants into their phospholipids (Lu et al, 2007;Wu et al, 2009;Drigo et al, 2010;Gschwendtner et al, 2011). Another large part (c. 9% of the total in the first sampling) of the total 13 C was detected in PLFA 16:1x5, mainly representing AMF (Olsson & Johnson, 2005;Denef et al, 2007).…”

“…It has been reported that carbon allocation within plants is strongly regulated by genotype and stage of development. Several studies (Milling et al, 2004;Götz et al, 2006;Griffiths et al, 2007;O'Callaghan et al, 2008;Weinert et al, 2009;Hannula et al, 2010) have provided information on the effects of transgenic crops on soil bacterial and fungal communities, but only a few have addressed the question from the carbon-partitioning perspective (Wu et al, 2009;Gschwendtner et al, 2011).…”

“…Use of phospholipid fatty acid analysis in combination with stable isotope probing (PLFA-SIP) has indicated that fungi are a very important group of organotrophic organisms in the rhizosphere and even inside roots receiving considerable amounts of plant-derived carbon (Butler et al, 2003;Lu et al, 2004;Wu et al, 2009;Gschwendtner et al, 2011). In addition, fungi are known to respond rapidly to the addition of easily degradable substrates such as root exudates (Broeckling et al, 2008;De Graaff et al, 2010).…”

Impact of Bt-transgenic rice (SHK601) on soil ecosystems in the rhizosphere during crop development

“…These results revealed that Bt-transgenic rice had little effect on dominant microorganisms essential for long-term sustainability of soil ecosystems. Wu et al (2009) studied soil microbial communities in the rhizosphere of Bt and non-Bt rice using phospholipid fatty acid analysis, and found that Bt rice had no persistent effect on microbial community composition in the rhizosphere. Other studies showed that the effects of GM plants on microbial communities are subject more to seasonal variations or to other environmental factors than to expression of Cry or other proteins (Fang et al 2005, Icoz et al 2008.…”

Impacts of the transgenic CrylAc and CpTI insect-resistant cotton SGK321 on selected soil enzyme activities in the rhizosphere

“…60, 2014, No. 9: 401-406 Plant Soil Environ. phospholipid fatty acid analysis with 13 C labeling (Wu et al 2009), denaturing gradient gel electrophoresis (Na et al 2011), terminal restriction fragment length polymorphism (Hannula et al 2012), next generation sequencing (Barriuso et al 2012). Only one report stated that the structures of soil bacterial communities of transgenic Bt maize, as determined by the single strand conformation polymorphism (SSCP), showed a significant difference (Baumgarte and Tebbe 2005).…”