Editors' ChoicePlant biology

Rice that tolerates a chill

Sci. Signal.  31 Mar 2015:
Vol. 8, Issue 370, pp. ec76
DOI: 10.1126/scisignal.aab2152

Rice is a major food source. Asian cultivated rice is primarily from two subspecies of Oryza sativa: indica, which produces a high yield but requires warm tropical temperatures, and japonica, which has a lower yield but can tolerate lower temperatures. Ma et al. identified a single nucleotide variation in the gene COLD1 (CHILLING-TOLERANCE DIVERGENCE 1) that was responsible for the difference in cold tolerance between indica and japonica (see Manishankar and Kudla). In the cold-tolerant japonica COLD1 had a lysine residue, whereas the cold-intolerant indica had either a methionine or threonine. Overexpression, knockdown, and mutation analysis confirmed that this variation in COLD1 was responsible for the difference in growth and survival after exposure to cold temperatures. COLD1 is predicted to have nine transmembrane domains and is related to the Arabidopsis orthologs GTG1 and GTG2, which interact with the α subunit of G proteins (RGA1) and function as guanosine triphosphatase (GTPase)–activating proteins. A yeast two-hybrid assay, immunoprecipitation experiments with transgenic plants expressing tagged versions of COLD1 and RGA1, and bimolecular fluorescence complementation assays revealed an interaction between COLD1 and RGA1. However, only the japonica COLD1 enhanced the GTPase activity of RGA1 in vitro; indica COLD1 inhibited RGA1 GTPase activity in vitro. Consistent with the enhancement of RGA1 activity by COLD1 in cold tolerance, RGA1 mutant japonica plants exhibited reduced survival when grown in cold conditions. Expression of COLD1 and RGA1 in Xenopus oocytes showed that COLD1 functions as an ion channel, with japonica, but not indica, COLD1 producing an inward current when coexpressed with RGA1. Analysis of calcium signals in plants showed that cold shock induced a stronger calcium signal in japonica than in indica and that the response depended on COLD1 and its magnitude depended on RGA1. This study provides a molecular clue to the differences in cold tolerance for two common strains of rice, which could lead to improved crop yield through molecular breeding techniques.

Y. Ma, X. Dai, Y. Xu, W. Luo, X. Zheng, D. Zeng, Y. Pan, X. Lin, H. Liu, D. Zhang, J. Xiao, X. Guo, S. Xu, Y. Niu, J. Jin, H. Zhang, X. Xu, L. Li, W. Wang, Q. Qian, S. Ge, K. Chong, COLD1 confers chilling tolerance in rice. Cell 160, 1209–1221 (2015). [PubMed]

P. Manishankar, J. Kudla, Cold tolerance encoded in one SNP. Cell 160, 1045–1046 (2015). [PubMed]