The tomato OST1–VOZ1 module regulates drought-mediated flowering

Abstract

Flowering is a critical agricultural trait that substantially affects tomato fruit yield. Although drought stress influences flowering time, the molecular mechanism underlying drought-regulated flowering in tomato remains elusive. In this study, we demonstrated that loss of function of tomato OPEN STOMATA 1 (SlOST1), a protein kinase essential for abscisic acid (ABA) signaling and abiotic stress responses, lowers the tolerance of tomato plants to drought stress. slost1 mutants also exhibited a late flowering phenotype under both normal and drought stress conditions. We also established that SlOST1 directly interacts with and phosphorylates the NAC-type transcription factor VASCULAR PLANT ONE-ZINC FINGER 1 (SlVOZ1), at residue serine 67, thereby enhancing its stability and nuclear translocation in an ABA-dependent manner. Moreover, we uncovered several SlVOZ1 binding motifs from DNA affinity purification sequencing analyses and revealed that SlVOZ1 can directly bind to the promoter of the major flowering-integrator gene SINGLE FLOWER TRUSS (SFT) to promote tomato flowering transition in response to drought. Collectively, our data uncover the essential role of the SlOST1-SlVOZ1 module in regulating flowering in response to drought stress in tomato and offer insights into a novel strategy to balance drought stress response and flowering.

ABA activated SnRK2 kinases: an emerging role in plant growth and physiology

“… 15 Hwang et al (2019) 16 demonstrated that the other bZIP-type transcription factors, ABF3 and ABF4, promote flowering by increasing SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) expression in response to drought, while the tomato OST1 kinase enhances flowering by phosphorylating the NAC-type transcription factor VOZ1 in under drought stress conditions. 17 FLOWERING LOCUS C (FLC) transcription is activated by the transcription factor ABSCISIC ACID INSENSITIVE MUTANT 5 (ABI5) , which binds directly to its promoter. Thus, the ABI5-FLC module negatively regulates flowering time in Arabidopsis and the ABA-activated SnRK2.6 (OST1) is essential for this regulation.…”

Burning questions for a warming and changing world: 15 unknowns in plant abiotic stress

“…They encode a class of small globular proteins that move long-distance through phloem vessels at the shoot apex to cause transcriptional reprogramming of meristem cells and floral specification of new primordia. While florigen’s transcriptional activation usually occurs upon perception of critical daylengths, studies in Arabidopsis, rice, and tomato further point to the contribution of water deficit signals ( Riboni et al, 2013 ; Du et al, 2018 ; Chong et al, 2022 ). Transcriptional upregulation of florigen genes in response to water deficit appears to be necessary and sufficient to cause DE in these species, despite their evolutionary separation.…”

Regulatory network established by transcription factors transmits drought stress signals in plant

“…In rice, the fact that OsSnRK1α interacts and phosphorylates ERF family TF OsEBP89 has also been observed, despite that the effect of phosphorylation remains to be determined (Zhang et al 2020b). Recently, it was demonstrated that phosphorylation of SlVOZ1 by SlOST1 promoted both stability and nuclear translocation of SlVOZ1 in tomato (Chong et al 2022). In addition to SnRK2 and CPK, other kinases such as MAK kinases, GSK3-like kinases (BIN2), could be responsible for phosphorylation of TFs to affect their stability and transcriptional activity (Table 1).…”

“…More evidences are required to prove whether they are common targets regulated by drought in different plant species. Interestingly, recent studies revealed that direct activation of SIN-GLE FLOWER TRUSS (SFT) by SlVOZ1 is essential for drought-accelerated flowering, known as a drought escape (DE) response (Chong et al 2022).…”