English

Abstract

Chia (Salvia hispanica), originated in Mexico, has outstanding nutritional and health-promoting values, but it is the only ancient American Indian staple crop failed in introduction to the Old Continents. After the rediscovery and revival of chia as a new crop in recent years, the short-day (SD) habit is a crucial limitation for its worldwide cultivation. The circadian oscillator GIGNATEA (GI) is an important transcription factor regulating flowering time through photoperiod-pathway. In this study, we cloned the full-length cDNAs of two GI genes from chia, and analyzed the molecular characteristics of the genes and the encoded proteins. Alternative transcription initiation sites, alternative poly A tailing sites, and 5’-UTR intron retention exist in some of their mRNAs. The origin of GI gene accompanied with the transition from aquatic to terrestrial habits during plant evolution. GI duplication events occurred at order, family and genus levels in angiosperms. ShGI-1 and ShGI-2 were similar to each other in organ specificity with peak expression in small buds. In mature leaf, ShGI-2 is dominant over ShGI-1 in terms of expression level with highest expression in the afternoon, but on the Autumnal Equinox day ShGI-1 is dominant over ShGI-2 with peaks at noon and in the evening. KT, BR, GA3 and IAA upregulated the expression of ShGI-1 and ShGI-2 in long-days (LDs) and inhibited their expression in SDs, with GA3 being the most effective phytohormone. Under most abiotic stresses, ShGI expression fluctuated and returned to near-basal levels. ShGI expression was upregulated by low temperature. SA sharply upregulated ShGI expression after 24 h of treatment. This is the first report of GI genes from the order Lamiales, which will promote the dissection of flowering mechanism of chia and other Lamiales plants, enrich the evolution and expression characteristics of plant GIs, and promote the study on interaction between photoperiod and hormone pathways in flowering time control. © 2021 Friends Science Publishers