Evolution of the miR5200-FLOWERING LOCUS T flowering time regulon in the temperate grass subfamily Pooideae

The Pivotal Role of Noncoding RNAs in Flowering Time Regulation

Noncoding RNAs constitute a substantial portion of the transcriptome and play pivotal roles in plant growth and development. Among these processes, flowering stands out as a crucial trait, ensuring reproductive success and seed set, and is meticulously controlled by genetic and environmental factors. With remarkable advancements in the identification and characterization of noncoding RNAs in plants, it has become evident that noncoding RNAs are intricately linked to the regulation of flowering time. In this article, we present an overview of the classification of plant noncoding RNAs and delve into their functions in the regulation of flowering time. Furthermore, we review their molecular mechanisms and their involvement in flowering pathways. Our comprehensive review enhances the understanding of how noncoding RNAs contribute to the regulation of flowering time and sheds light on their potential implications in crop breeding.

Role of plant microRNAs and their corresponding pathways in fluctuating light conditions

In recent years, it has been established that microRNAs (miRNAs) are critical for various plant physiological regulations in numerous species. Next-generation sequencing technologies have aided to our understandings related to the critical role of miRNAs during environmental stress conditions and plant development. Light influences not just miRNA accumulation but also their biological activities via regulating miRNA gene transcription, biosynthesis, and RNA-induced silencing complex (RISC) activity. Light-regulated routes, processes, and activities can all be affected by miRNAs. Here, we will explore how light affects miRNA gene expression and how conserved and novel miRNAs exhibit altered expression across different plant species in response to variable light quality. Here, we will mainly discuss recent advances in understanding how miRNAs are involved in photomorphogenesis, and photoperiod-dependent plant biological processes such as cell proliferation, metabolism, chlorophyll pigment synthesis and axillary bud growth. The review concludes by presenting future prospects via hoping that light-responsive miRNAs can be exploited in a better way to engineer economically important crops to ensure future food security.

The wild grass Brachypodium distachyon as a developmental model system

The arrival of cheap and high-throughput sequencing paired with efficient gene editing technologies allows us to use non-traditional model systems and mechanistically approach biological phenomena beyond what was conceivable just a decade ago. Venturing into different model systems enables us to explore for example clade-specific environmental responses to changing climates or the genetics and development of clade-specific organs, tissues and cell types. We-both early career researchers working with the wild grass model Brachypodium distachyon-want to use this review to (1) highlight why we think B. distachyon is a fantastic grass developmental model system, (2) summarize the tools and resources that have enabled discoveries made in B. distachyon, and (3) discuss a handful of developmental biology vignettes made possible by using B. distachyon as a model system. Finally, we want to conclude by (4) relating our personal stories with this emerging model system and (5) share what we think is important to consider before starting work with an emerging model system.

Small RNA sequencing revealed various microRNAs involved in ethylene-triggered flowering process in Aechmea fasciata

Ethylene-triggered flowering is a common phenomenon in plants of the family Bromeliaceae, but its molecular mechanism remains unclear. As a classical group of small RNAs, microRNAs play an essential role in the regulation of flowering. In this study, we found that various miRNAs participate in the ethylene-triggered flowering process in Aechmea fasciata via small RNA sequencing using juvenile and adult plants treated with ethylene for 24 hours. Finally, 63 known miRNAs, 52 novel miRNAs and 1721 target genes were identified or predicted. Expression changes of specific miRNAs were validated by qRT-PCR and northern blotting. Some predicted targets, including SPL, GAMYB and ARF, were verified in RLM-RACE experiments. Gene Ontology (GO) and KEGG analysis showed that numerous developmental and RNA-related processes were enriched. Integrated analysis of the transcriptomic data with small RNA sequencing revealed that numerous miRNAs and targets involved in ethylene-triggered flowering in A. fasciata. Our study is helpful for illuminating the molecular basis of the ethylene-triggered flowering phenomenon in Bromeliaceae.

Divergent roles of FT-like 9 in flowering transition under different day lengths in Brachypodium distachyon

Timing of reproductive transition is precisely modulated by environmental cues in flowering plants. Facultative long-day plants, including Arabidopsis and temperate grasses, trigger rapid flowering in long-day conditions (LDs) and delay flowering under short-day conditions (SDs). Here, we characterize a SD-induced FLOWERING LOCUS T ortholog, FT-like 9 (FTL9), that promotes flowering in SDs but inhibits flowering in LDs in Brachypodium distachyon. Mechanistically, like photoperiod-inductive FT1, FTL9 can interact with FD1 to form a flowering activation complex (FAC), but the floral initiation efficiency of FTL9-FAC is much lower than that of FT1-FAC, thereby resulting in a positive role for FTL9 in promoting floral transition when FT1 is not expressed, but a dominant-negative role when FT1 accumulates significantly. We also find that CONSTANS 1 (CO1) can suppress FTL9 in addition to stimulate FT1 to enhance accelerated flowering under LDs. Our findings on the antagonistic functions of FTL9 under different day-length environments will contribute to understanding the multifaceted roles of FT in fine-tune modulation of photoperiodic flowering in plants.

Plant flowering time is modified by day length. Here the authors show that the model grass Brachypodium distachyon expresses different homologs of FT in short and long days to produce floral activator complexes with altered activities contributing to photoperiod-dependence of flowering time.

Natural variation in Brassica FT homeologs influences multiple agronomic traits including flowering time, silique shape, oil profile, stomatal morphology and plant height in B. juncea

Natural structural variants of regulatory proteins causing quantitative phenotypic consequences have not been reported in plants. Herein, we show that 28 natural structural variants of FT homeologs, isolated from 6 species of Brassica, differ with respect to amino-acid substitutions in regions critical for interactions with FD and represent two evolutionarily distinct categories. Analysis of structural models of selected candidates from Brassica juncea (BjuFT_AAMF1) and Brassica napus (BnaFT_CCLF) predicted stronger binding between BjuFT and Arabidopsis thaliana FD. Over-expression of BjuFT and BnaFT in wild type and ft-10 mutant backgrounds of Arabidopsis validated higher potency of BjuFT in triggering floral transition. Analysis of gain-of-function and artificial miRNA mediated silenced lines of B. juncea implicated Brassica FT in multiple agronomic traits beyond flowering, consistent with a pleiotropic effect. Several dependent and independent traits such as lateral branching, silique shape, seed size, oil-profile, stomatal morphology and plant height were found altered in mutant lines. Enhanced FT levels caused early flowering, which in turn was positively correlated to a higher proportion of desirable fatty acids (PUFA). However, higher FT levels also resulted in altered silique shape and reduced seed size, suggesting trait trade-offs. Modulation of FT levels for achieving optimal balance of trait values and parsing pair-wise interactions among a reportoire of regulatory protein homeologs in polyploid genomes are indeed future areas of crop research.

Transcriptome analysis reveals new microRNAs-mediated pathway involved in anther development in male sterile wheat

Background

337S is a novel bi-pole-photo-thermo-sensitive genic male sterile line in wheat, and sensitive to both long day length/high temperature and short day length/low temperature condition. Although the regulatory function of MicroRNAs (miRNAs) in reproductive development has been increasingly studied, their roles in pre-meiotic and meiotic cells formation of plants have not been clearly explored. Here, we explored the roles of miRNAs in regulating male sterility of 337S at short day length/low temperature condition.

Results

Small RNA sequencing and degradome analyses were employed to identify miRNAs and their targets in the 337S whose meiotic cells collapsed rapidly during male meiotic prophase, resulting in failure of meiosis at SL condition. A total of 102 unique miRNAs were detected. Noticeably, the largest miRNA family was MiR1122. The target CCR4-associated factor 1 (CAF1) of miR2275, a subunit of the Carbon Catabolite Repressed 4-Negative on TATA-less (CCR4-NOT) complex, contributes to the process of early meiosis, and was first identified here. Further studies showed that the expression of several pivotal anther-related miRNAs was altered in 337S at SL condition, especially tae-miR1127a, which may be related to male sterility of 337S. Here, we also identified a new member of SWI/SNF factors SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily A, member 3-like 3 (SMARCA3L3) targeted by tae-miR1127a, whose function might be involved in faithful progression of meiosis in male reproductive cells.

Conclusion

The miRNA-target interactions of tae-miR2275-CAF1 and tae-miR1127a-SMARCA3L3 might be involved in regulating male fertility in 337S. Our results also implied that multiple roles for SMARCA3L3 and CAF1 in DNA repair and transcriptional regulation jointly orchestrated a tight and orderly system for maintaining chromatin and genome integrity during meiosis.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4727-5) contains supplementary material, which is available to authorized users.