Drought Tolerance Conferred to Sugarcane by Association with Gluconacetobacter diazotrophicus: A Transcriptomic View of Hormone Pathways

Abstract

Sugarcane interacts with particular types of beneficial nitrogen-fixing bacteria that provide fixed-nitrogen and plant growth hormones to host plants, promoting an increase in plant biomass. Other benefits, as enhanced tolerance to abiotic stresses have been reported to some diazotrophs. Here we aim to study the effects of the association between the diazotroph Gluconacetobacter diazotrophicus PAL5 and sugarcane cv. SP70-1143 during water depletion by characterizing differential transcriptome profiles of sugarcane. RNA-seq libraries were generated from roots and shoots of sugarcane plants free of endophytes that were inoculated with G. diazotrophicus and subjected to water depletion for 3 days. A sugarcane reference transcriptome was constructed and used for the identification of differentially expressed transcripts. The differential profile of non-inoculated SP70-1143 suggests that it responds to water deficit stress by the activation of drought-responsive markers and hormone pathways, as ABA and Ethylene. qRT-PCR revealed that root samples had higher levels of G. diazotrophicus 3 days after water deficit, compared to roots of inoculated plants watered normally. With prolonged drought only inoculated plants survived, indicating that SP70-1143 plants colonized with G. diazotrophicus become more tolerant to drought stress than non-inoculated plants. Strengthening this hypothesis, several gene expression responses to drought were inactivated or regulated in an opposite manner, especially in roots, when plants were colonized by the bacteria. The data suggests that colonized roots would not be suffering from stress in the same way as non-inoculated plants. On the other hand, shoots specifically activate ABA-dependent signaling genes, which could act as key elements in the drought resistance conferred by G. diazotrophicus to SP70-1143. This work reports for the first time the involvement of G. diazotrophicus in the promotion of drought-tolerance to sugarcane cv. SP70-1143, and it describes the initial molecular events that may trigger the increased drought tolerance in the host plant.

De novo transcriptome assembly of sugarcane leaves submitted to prolonged water-deficit stress

“…However, most transcriptome studies (e.g., microarrays, SAGE, cDNA-AFLP) in sugarcane (Rodrigues et al, 2009;Kido et al, 2012;Vantini et al, 2015), as well as the study of Vargas et al (2014) using the RNA-Seq technology, have evaluated the effect of short-term water stress (usually the complete absence of irrigation) and of water stress in young plants. These designs can lead to poorly acceptable results regarding the drought sensitivity or tolerance of plants under real field conditions where water restriction usually lasts for several months.…”

Regenerasi Tanaman dari Kalus Tebu yang Diiradiasi Sinar Gamma pada Medium dengan PEG 6000

“…Varietas yang toleran cekaman dapat diperoleh melalui persilangan antar tetua, melalui tranfer gen (Vantini et al, 2015), memanfaatkan bakteri endofit (Vargas et al, 2014), seleksi tanaman menggunakan medium NaCl untuk toleransi terhadap cekaman salinitas, dan PEG atau mannitol untuk toleransi terhadap cekaman kekeringan (Errabii et al, 2008;Begum et al, 2011;Khumar et al, 2011). Melalui teknik in vitro, kutivar yang toleran terhadap cekaman kekeringan dapat diperoleh dengan meregenerasikan tanaman dari kalus yang memiliki keragaman genetik pada medium seleksi menggunakan PEG (Begum et al, 2011).…”

Endophytic bacteria affect sugarcane physiology without changing plant growth

“…Plants were under non-limiting conditions in this study and we should take into account that any advantage associated to inoculation may occur under stress condition (Vargas et al 2014). For instance, II or untreated (control).…”