The MKKK62-MKK3-MAPK7/14 module negatively regulates seed dormancy in rice

Abstract

BackgroundSeed dormancy directly affects the phenotype of pre-harvest sprouting, and ultimately affects the quality and yield of rice seeds. Although many genes controlling seed dormancy have been cloned from cereals, the regulatory mechanisms controlling this process are complex, and much remains unknown. The MAPK cascade is involved in many signal transduction pathways. Recently, MKK3 has been reported to be involved in the regulation of seed dormancy, but its mechanism of action is unclear.ResultsWe found that MKKK62-overexpressing rice lines (OE) lost seed dormancy. Further analyses showed that the abscisic acid (ABA) sensitivity of OE lines was decreased. In yeast two-hybrid experiments, MKKK62 interacted with MKK3, and MKK3 interacted with MAPK7 and MAPK14. Knock-out experiments confirmed that MKK3, MAPK7, and MAPK14 were involved in the regulation of seed dormancy. The OE lines showed decreased transcript levels of OsMFT, a homolog of a gene that controls seed dormancy in wheat. The up-regulation of OsMFT in MKK3-knockout lines (OE/mkk3) and MAPK7/14-knockout lines (OE/mapk7/mapk14) indicated that the MKKK62-MKK3-MAPK7/MAPK14 system controlled seed dormancy by regulating the transcription of OsMFT.ConclusionOur results showed that MKKK62 negatively controls seed dormancy in rice, and that during the germination stage and the late stage of seed maturation, ABA sensitivity and OsMFT transcription are negatively controlled by MKKK62. Our results have clarified the entire MAPK cascade controlling seed dormancy in rice. Together, these results indicate that protein modification by phosphorylation plays a key role in controlling seed dormancy.Electronic supplementary materialThe online version of this article (10.1186/s12284-018-0260-z) contains supplementary material, which is available to authorized users.

Update on the Roles of Rice MAPK Cascades

“…Of the ten functionally studied OsMAPKs, OsMAPK3, OsMAPK4 and OsMAPK6 are T-E-Y subtype MAPKs, the other seven (OsMAPK7, OsMAPK14, OsMAPK16, OsMAPK17-1, OsMAPK17-2, OsMAPK20-4, OsMAPK20-5) are T-D-Y subtype MAPKs. Only a few of them are validated as substrates and can be phosphorylated by upstream OsMAPKKs, such as OsMAPK3, OsMAPK6, OsMAPK7, and OsMAPK14 [24,28,30,33].…”

“…OsMAPKKK10-OsMAPKK4-OsMAPK6 cascade plays critical roles in rice grain morphogenesis, rice panicle development, BR homeostasis and signaling pathway [17][18][19]. OsMAPKKK62-OsMAPKK3-OsMAPK7/14 cascades affect ABA signal transduction, ABA content and seed dormancy [24]. OsMAPKKK63-OsMAPKK1-OsMAPK4 cascade regulates salt stress response [25,26].…”

“…In turn, a MAPKK can phosphorylate and activate several MAPKs, including OsMAPKK1 can target OsMAPK4 and OsMAPK6 [26,54,60], OsMAPKK10-2 phosphorylates OsMAPK3 and OsMAPK6 [27][28][29], OsMAPKK3 interacts with OsMAPK6, OsMAPK7 and OsMAPK14 [24,30,54,60], OsMAPKK6 associates with OsMAPK3, OsMAPK4 and OsMAPK6 [29,54,60,61]. The present data uncover that a MAPKK can interact with several MAPKs to play roles in different physiological processes.…”

“…[12][13][14][15]27,28,40,43,48,49]. The established OsMAPKKK62-Os-MAPKK3-OsMAPK7/14 cascades are regulated by ABA, while the OsMAPKKK10-OsMAPKK4-Os-MAPK6 cascade can regulate BR and CK signal transduction [17][18][19]24].…”

Prospects for the accelerated improvement of the resilient crop quinoa

“…Mitogen-activated Protein Kinase Kinase 3 ( MKK3 ) is the causal gene of the major grain dormancy quantitative trait loci (QTLs) Qsd2-AK ( SD2 ) and PHS1 in barley and wheat, respectively ( Nakamura et al , 2016 ; Torada et al , 2016 ). In rice, the MKKK62–MKK3–MAPK7/14 module controls seed dormancy via regulating OsMFT transcription ( Mao et al , 2019 ). Exchange of the evolutionarily conserved amino acid N260 to T260 in MKK3 adapts barley to wet growth conditions in East Asia ( Nakamura et al , 2016 ).…”