Down‐regulation of GIGANTEA‐like genes increases plant growth and salt stress tolerance in poplar

Abstract

SummaryThe flowering time regulator GIGANTEA (GI) connects networks involved in developmental stage transitions and environmental stress responses in Arabidopsis. However, little is known about the role of GI in growth, development and responses to environmental challenges in the perennial plant poplar. Here, we identified and functionally characterized three GI‐like genes (PagGIa, PagGIb and PagGIc) from poplar (Populus alba × Populus glandulosa). PagGIs are predominantly nuclear localized and their transcripts are rhythmically expressed, with a peak around zeitgeber time 12 under long‐day conditions. Overexpressing PagGIs in wild‐type (WT) Arabidopsis induced early flowering and salt sensitivity, while overexpressing PagGIs in the gi‐2 mutant completely or partially rescued its delayed flowering and enhanced salt tolerance phenotypes. Furthermore, the PagGIs‐PagSOS2 complexes inhibited PagSOS2‐regulated phosphorylation of PagSOS1 in the absence of stress, whereas these inhibitions were eliminated due to the degradation of PagGIs under salt stress. Down‐regulation of PagGIs by RNA interference led to vigorous growth, higher biomass and enhanced salt stress tolerance in transgenic poplar plants. Taken together, these results indicate that several functions of Arabidopsis GI are conserved in its poplar orthologues, and they lay the foundation for developing new approaches to producing salt‐tolerant trees for sustainable development on marginal lands worldwide.

GIGANTEA‐like genes control seasonal growth cessation in Populus

“…Recently, three GI ‐like genes from P. alba × glandulosa have been described (Ke et al ., ). By searching the genome sequences of P. trichocarpa ( Pt ) and our model tree P. tremula × tremuloides ( Ptt ), we found that both genomes contain two highly similar GI ‐like genes, which we call Pt/PttGI and Pt/PttGI‐Like ( Pt/PttGIL ) (Fig.…”

“…This is a much stronger response than that reported when PttFT or PttCO is down‐regulated (Bohlenius et al ., ). It was recently found that down‐regulation of GI ‐like genes causes increased growth and confers salt stress tolerance in P. alba × glandulosa (Ke et al ., ). These apparently contradictory results may be attributable to a less efficient GI down‐regulation in the P. alba × glandulosa trees, as we also see increased growth rates in those of our PttGIRNAi transgenic trees that have more modest reductions in PttGI expression (results not shown).…”

“…Multiple phytohormones have been shown to be involved in branching control, such as auxins, cytokinins, GAs and strigolactones (Ongaro & Leyser, ). Interestingly, some of early auxin response genes were significantly higher in poplar GIRNAi plants (Ke et al ., ). Furthermore, the dwarfed phenotype of the PttGIRNAi plants is highly suggestive of a role for GI in the control of GA metabolism or signaling.…”

“…GIGANTEA orthologs have been described in many plant species and appear to have similar roles in the photoperiodic regulation of flowering time and in salt stress tolerance (Hecht et al ., ; Izawa et al ., ; Watanabe et al ., ; Bendix et al ., ; Xie et al ., ; Kim et al ., ; Ke et al ., ; Tang et al ., ). Genetic variants at GI loci have been associated with phenology traits in a number of tree species, including both angiosperms (Rohde et al ., ; Keller et al ., ; Alberto et al ., ) and gymnosperms (Holliday et al ., ; Chen et al ., ).…”

Bacterial and fungal communities are differentially modified by melatonin in agricultural soils under abiotic stress

“…Both cadmium toxicity and soil salinization cause a dramatic increase in cellular levels of highly destructive reactive oxygen species (ROS) as well as inhibiting the activities of ROS scavenging enzymes in microbes (Tanaka et al, 2006, Achard-Joris et al, 2007, Hossain et al, 2012), thus decreasing crop yield. Globally, up to 2 million hectares of agricultural land are negatively impacted by salinization each year (Bencherif et al, 2015, Ke et al, 2017). Alterations to the soil microbial community can have important repercussions in agricultural settings, where microbes (both soil bacteria and fungi) are critical drivers of soil health and agricultural crop productivity (Mau et al, 2019, Zhang et al, 2019).…”