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

Qingbo Ke,Ho Soo Kim,Dae‐Jin Yun,Zhi Wang,Bingcheng Xu,Sang‐Soo Kwak,Xiping Deng,Chang Yoon Ji,Haeng‐Soon Lee,Jae Cheol Jeong,Young‐Im Choi

doi:10.1111/pbi.12628

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.

Highlights

The worldwide population is expected to reach between 9.6 and 12.3 billion by 2100, which presents challenges to energy security, economic growth and environmental protection (Gerland et al, 2014)
Phylogenetic analysis of the deduced plant GI amino acid sequences from 12 species showed that PagGIa, b and c are closely clustered with other dicot GI homologues and belong to the same subgroup as AtGI (Figure 1a)
Comparison of the deduced amino acid sequences of AtGI and the PagGI genes revealed that the regions for their nuclear localization are conserved among Arabidopsis and poplar GI, which contain four clusters of basic amino acids similar to the clusters identified in established bipartite NLSs in other nuclear proteins (Huq et al, 2000) (Figure 1b)

Summary

Introduction

The worldwide population is expected to reach between 9.6 and 12.3 billion by 2100, which presents challenges to energy security, economic growth and environmental protection (Gerland et al, 2014). Environmental problems such as global warming, drought and salinity severely limit agricultural and forest productivity (Lobell and Gourdji, 2012; Sivakumar et al, 2005). The salt stress response is controlled by many genes that function through complex genetic regulatory networks. The SOS2–SOS3 complex phosphorylates and activates the transport activity of the SOS1 antiporter (Guo et al, 2001; Ji et al, 2013; Zhu, 2000).

Results

Discussion

Conclusion