Differential effects of cadmium and chromium on growth, photosynthetic activity, and metal uptake of Linum usitatissimum in association with Glomus intraradices.

The current study was aimed at analyzing the differential effects of heavy metals (cadmium and chromium) and mycorrhizal fungus; Glomus intraradices on growth, chlorophyll content, proline production, and metal accumulation in flax plant (Linum usitatissimum L.). Heavy metal accumulation rate in flax varied from 90 to 95 % for Cd and 61-84 % for Cr at a concentration range of 250 to 500 ppm for both metals in 24 days of experiment. Growth and photosynthetic activity of flax reduced to an average of 21 and 45 %, respectively. However, inoculation of G. intraradices significantly increased the plant biomass even under metal stressed conditions. Additionally, mycorrhizal association also assists the Cd and Cr increased uptake by 23 and 33 %, respectively. Due to metal stress, chlorophyll contents were decreased by 27 and 45 %, while 84 and 71 % increased proline content was observed under Cd and Cr stress, respectively. The present results clearly signify the differential response and potential of flax plant towards heavy metal tolerance and accumulation that can further increase with mycorrhizal fungus.

A thaumatin-like protein gene involved in cotton fiber secondary cell wall development enhances resistance against Verticillium dahliae and other stresses in transgenic tobacco.

For the first time, a sea-island cotton (Gossypium barbadense L.) thaumatin-like protein gene (GbTLP1) with a potential role in secondary cell wall development has been overexpressed in tobacco to elucidate its function. The presence of the transgene was verified by Southern blotting and higher expression levels of GbTLP1 in transgenic tobacco plants were revealed by reverse-transcription and quantitative real-time polymerase chain reaction analyses. Transgenic plants with constitutively higher expression of the GbTLP1 showed enhanced resistance against different stress agents, particularly, its performance against Verticillium dahliae was exceptional. Transgenic tobacco plants also exhibited considerable resistance against Fusarium oxysporum and some abiotic stresses including salinity and drought. In this experiment, transgenic plants without GbTLP1 expression were also used as controls, which behaved similar to non-transgenic control plants. Overexpression of GbTLP1 had no significant deleterious effect on plant growth except that flowering was delayed for 3-5 weeks. The apparent pleiotropic effect of this novel gene has given us insight to the plant defense mechanism.