Rongcheng Lin’s research while affiliated with Chinese Academy of Sciences and other places

Red and blue lights are the most effective spectral components absorbed by plants and are typically applied in a constant spectrum in plant factory agricultural practices. Research and application of non‐constant light modes are relatively rare. In this study, we examined the impacts of varying blue light photon intensity and durations at 5‐, 15‐, 30‐, and 45‐min intervals of intermittent exposure on the growth and development of lettuce (Lactuca sativa) in plant factories while maintaining a constant red light photon flux and daily light integral (DLI). Compared to the constant light condition, intermittent blue light irradiation treatments accelerated the emergence of the leafy head trait in lettuce without compromising photosynthetic capacity and biomass. Specifically, intermittent blue light treatment with 15‐min intervals led to a reduction of 8 days in the time needed for half of the lettuce plants to reach the heading stage. Furthermore, the petiole bending angle in treated lettuce was just 70.2% of that observed under constant light conditions, with strong correlations between multiple hormone levels and bending angle in petioles. Transcriptome sequencing analyses revealed significant differential expression of signaling‐related genes between constant and intermittent blue light treatments. The transient and dynamic expression of light‐responsive and hormone metabolism‐related genes indicated that 15‐min intermittent blue light exposure better maintained the rhythmic differential expression of response genes, leading to different hormone accumulations and consequently accelerating the development of leafy heads.

Light is an essential environmental factor that facilitates the robust upward growth of post-germinative seedlings emerging from buried seeds that is partly mediated by the photoreceptors. Salinity stress hampers plant growth and development and reduces yield. However, the involvement and regulatory role of photoreceptors and light signaling factors to salt stress are largely unknown. Here, we report that mutants of the phytochrome B (phyB) photoreceptor showed reduced sensitivity to salt-inhibited hypocotyl elongation in darkness, and that PHYTOCHROME-INTERACTING FACTOR 3 (PIF3) acts downstream of phyB in regulating this process in Arabidopsis thaliana. We also show that SALT OVERLY SENSITIVE 2 (SOS2) regulates phyB protein accumulation under salt stress in darkness. Surprisingly, salt treatment induces phyB nuclear body formation in darkness. Moreover, we found that the phosphorylation at residue Ser-86 of phyB is essential for its function, and the scaffold protein 14-3-3κ is involved in the regulation of phyB under salt stress in darkness. Taken together, our study reveals a regulatory role of the phyB–PIF3 module in mediating post-germination growth in darkness in response to salt stress.

Seed dormancy enables plants to delay germination until conditions are favorable for the survival of the next generation. Seed dormancy and germination are controlled by a combination of external and internal signals, in which light and ethylene act as critical regulators. However, how light and ethylene are interlinked to control these two processes remains to be investigated. Here, we show that ethylene and its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), promote seed germination under light. Light facilitates the conversion of ACC to ethylene, in which phytochrome B (phyB) and FAR-RED ELONGATED HYPOCOTYL3 (FHY3) are functionally required. ACC oxidases (ACOs) catalyze the conversion of ACC to ethylene, among which ACO1 is specifically and predominantly expressed in imbibed seeds. Ethylene induces FHY3 protein accumulation in imbibed seeds, whereby FHY3 directly binds to ACO1 promoter and specifically mediates light-promoted ACO1 expression. Light promotes ACO1 protein accumulation. Overexpression of ACO1 significantly promotes seed germination, and almost completely restores the dormant defect of fhy3 loss-of-function mutants. In summary, this study reveals an ethylene-responsive regulatory cascade of phyB-FHY3-ACO1 that integrates external light input with internal factors to regulate seed dormancy and germination.

Plants, algae and photosynthetic bacteria convert light into chemical energy by means of photosynthesis, thus providing food and energy for most organisms on Earth. Photosynthetic pigments, including chlorophylls (Chls) and carotenoids, are essential components that absorb the light energy necessary to drive electron transport in photosynthesis. The biosynthesis of Chl shares several steps in common with the biosynthesis of other tetrapyrroles, including siroheme, heme and phycobilins. Given that many tetrapyrrole precursors possess photo‐oxidative properties that are deleterious to macromolecules and can lead to cell death, tetrapyrrole biosynthesis (TBS) requires stringent regulation under various developmental and environmental conditions. Thanks to decades of research on model plants and algae, we now have a deeper understanding of the regulatory mechanisms that underlie Chl synthesis, including (i) the many factors that control the activity and stability of TBS enzymes, (ii) the transcriptional and post‐translational regulation of the TBS pathway, and (iii) the complex roles of tetrapyrrole‐mediated retrograde signaling from chloroplasts to the cytoplasm and the nucleus. Based on these new findings, Chls and their derivatives will find broad applications in synthetic biology and agriculture in the future.

Supplementation with far-red light in controlled environment agriculture production can enhance yield by triggering the shade avoidance syndrome. However, the effectiveness of this yield enhancement can be further improved through intermittent far-red light supplementation. In this study, the effects are explored of varying far-red light photon intensities and intermittent exposure durations—specifically at 5, 15, 30, and 45 min intervals—on the growth and development of lettuce (Lactuca sativa) in plant factories, while maintaining a constant red light photon flux and daily light integral. The results showed that compared to constant far-red light, 30 min intermittent far-red light increased yield by 11.7% and the number of leaves and buds by 2.66. Furthermore, the various metrics demonstrated that intermittent far-red light supplementation enhanced the overall effectiveness of the far-red light treatment. This was validated by analyzing phytohormone content and the expression of genes related to hormone metabolism and transport at the tip of the lettuce stems. Transcriptome analysis revealed that the differences in gene expression between treatments were primarily concentrated in genes related to signaling, hormone metabolism, and transport. Weighted Gene Co-expression Network Analysis identified the co-expression modules associated with yield and quality. Additionally, dynamic expression analysis showed genes involved to far-red photoreception, response, and hormone metabolism and transport exhibited optimal rhythmic responses only under 30 min intermittent far-red light supplementation. This suggests that intermittent far-red light irradiation at 30 min intervals is the most effective for activating far-red light signaling influencing hormone metabolism and transport, thereby accelerating the growth of lettuce leaves and buds and ultimately increasing yield.

Light and temperature are two major environmental factors that affect growth and development of plants during their life cycle. Plants have evolved complex mechanisms to adapt to varying external environments. Here, we show that JASMONATE ZIM-domain protein 3 (JAZ3), a jasmonic acid signaling component, acts as a factor to integrate light and temperature in regulating seedling morphogenesis. JAZ3 overexpression transgenic lines display short hypocotyls under red, far-red, and blue light and warm temperature (28 °C) conditions compared to the wild type in Arabidopsis (Arabidopsis thaliana). We show that JAZ3 interacts with the transcription factor PHYTOCHROME-INTERACTING FACTOR4 (PIF4). Interestingly, JAZ3 spontaneously undergoes liquid-liquid phase separation (LLPS) in vitro and in vivo and promotes LLPS formation of PIF4. Moreover, transcriptomic analyses indicate that JAZ3 regulates the expression of genes involved in many biological processes, such as response to auxin, auxin-activated signaling pathway, regulation of growth, and response to red light. Finally, JAZ3 inhibits the transcriptional activation activity and binding ability of PIF4. Collectively, our study reveals a function and molecular mechanism of JAZ3 in regulating plant growth in response to environmental light and temperature.

Non-photochemical quenching (NPQ) plays a fundamental role in safely operating photosynthesis under low night temperatures (LNT). PsbS protein is essential for the rapid induction of NPQ, and its stability is often affected by adverse environmental conditions. However, the regulatory mechanism for the stability of PsbS or chloroplast proteins remains to be fully characterized. We showed that LNT decreased NPQ levels and SlPsbS protein abundance in tomato leaves. COP9 signalosome subunit 5A (SlCSN5A) facilitated SlPsbS ubiquitination and degradation in the cytosol. Further, tomato chloroplast vesiculation (SlCV) was activated by LNT. Under LNT, SlCV targeted the chloroplasts and induced the formation of CV-containing vesicles (CCVs) containing SlPsbS, which were exported from the chloroplasts. Subsequently, SlCV and SlPsbS contact SlCSN5A in the cytosol and are ubiquitinated and degraded. Genetic evidence demonstrated that overexpression of SlCV aggravated SlPsbS protein degradation, whereas silencing of SlCSN5 and SlCV delayed LNT-induced NPQ reduction and SlPsbS protein turnover. This study provides evidence that CSN5A is associated with chloroplast proteins, and reveals a ubiquitin-dependent degradation pathway of chloroplast proteins co-mediated by CV and CSN5A, thereby providing new insights into the regulation of chloroplast protein stability under stress conditions.