Abstract
CONSTANS (CO) is an important regulator of photoperiodic flowering and functions at a key position in the flowering regulatory network. Here, two CO homologs, MiCOL16A and MiCOL16B, were isolated from “SiJiMi” mango to elucidate the mechanisms controlling mango flowering. The MiCOL16A and MiCOL16B genes were highly expressed in the leaves and expressed at low levels in the buds and flowers. The expression levels of MiCOL16A and MiCOL16B increased during the flowering induction period but decreased during the flower organ development and flowering periods. The MiCOL16A gene was expressed in accordance with the circadian rhythm, and MiCOL16B expression was affected by diurnal variation, albeit not regularly. Both the MiCOL16A and MiCOL16B proteins were localized in the nucleus of cells and exerted transcriptional activity through their MR domains in yeast. Overexpression of both the MiCOL16A and MiCOL16B genes significantly repressed flowering in Arabidopsis under short-day (SD) and long-day (LD) conditions because they repressed the expression of AtFT and AtSOC1. This research also revealed that overexpression of MiCOL16A and MiCOL16B improved the salt and drought tolerance of Arabidopsis, conferring longer roots and higher survival rates to overexpression lines under drought and salt stress. Together, our results demonstrated that MiCOL16A and MiCOL16B not only regulate flowering but also play a role in the abiotic stress response in mango.
Highlights
In higher plants, floral transition is the process that describes the switch from the vegetative stage to the reproductive stage
Our results indicated that these two genes strongly influence the flowering and abiotic stress responses of mango
The results suggested that the two target genes were expressed in the leaFvoers tohfemtiasnsugoe-aspt eaclliftiecsteexdppreesrsioiodns.teTshtse, eqxRpTre–sPsiCoRn wpaatsteprnerofof rMmiCedO.LT1h6Ae rgersaudlutsasllhyowed thaitncMreiaCseOdLf1r6oAm vaengdetMatiivCeOgLro1w6Bthwtoertheeelxatperflesosreadl ininduacltliotnhpeetreiosdteadndtistshuenesd. eOcrneadseidfferent bra(nFicghuerse, 2tCh)e
Summary
Floral transition is the process that describes the switch from the vegetative stage to the reproductive stage. The time for this process is referred to as flowering time. The onset of flowering is regulated in a timely manner by an intricate network involving a series of regulatory pathways, such as gibberellin, photoperiod, autonomous, aging and vernalization pathways [1–3]. The E3 ubiquitin ligase-encoding gene HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES1 (HOS1) is involved in controlling the abundance of CO, and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1), as a flowering repressor, is regulated by cryptochromes (CRY) and promotes the proteolysis of CO in the dark [16,17]. Group I genes have one CO, CO-like, and TOC1 (CCT) domain and two B-box domains; group II genes have one B-box and one CCT domain; and group III genes have one B-box, one variant B-box and one CCT domain
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