Plant Physiology最新文献

Heat stress is a substantial and imminent threat to plant growth and development. Understanding its adverse effects on plant development at the molecular level is crucial for sustainable agriculture. However, the molecular mechanism underlying how heat stress causes developmental defects in flowers remains poorly understood. Here, we identified Indole-3-Acetic Acid 8 (IAA8), a repressor of auxin signaling, as a substrate of mitogen-activated protein kinases (MPKs) in Arabidopsis thaliana, and found that MPK-mediated phosphorylation of IAA8 inhibits flower development. MPKs phosphorylated three residues of IAA8: S74, T77, and S135. Interestingly, transgenic plants overexpressing a phospho-mimicking mutant of IAA8 (IAA8DDD OX) exhibited defective flower development due to high IAA8 levels. Furthermore, MPK-mediated phosphorylation inhibited IAA8 polyubiquitination, thereby significantly increasing its stability. Additionally, the expression of key transcription factors involved in flower development, such as bZIP and MYB genes, was significantly perturbed in the IAA8DDD OX plants. Collectively, our study demonstrates that heat stress inhibits flower development by perturbing the expression of flower development genes through the MPK-mediated phosphorylation of IAA8, suggesting that Aux/IAA phosphorylation enables plants to fine-tune their development in response to environmental stress.

In many eukaryotic algae, CO2 fixation by Rubisco is enhanced by a CO2-concentrating mechanism, which utilizes a Rubisco-rich organelle called the pyrenoid. The pyrenoid is traversed by a network of thylakoid membranes called pyrenoid tubules, which are proposed to deliver CO2. In the model alga Chlamydomonas (Chlamydomonas reinhardtii), the pyrenoid tubules have been proposed to be tethered to the Rubisco matrix by a bestrophin-like transmembrane protein, BST4. Here, we show that BST4 forms a complex that localizes to the pyrenoid tubules. A Chlamydomonas mutant impaired in the accumulation of BST4 (bst4) formed normal pyrenoid tubules, and heterologous expression of BST4 in Arabidopsis (Arabidopsis thaliana) did not lead to the incorporation of thylakoids into a reconstituted Rubisco condensate. Chlamydomonas bst4 mutants did not show impaired growth under continuous light at air level CO2 but were impaired in their growth under fluctuating light. By quantifying the non-photochemical quenching (NPQ) of chlorophyll fluorescence, we propose that bst4 has a transiently lower thylakoid lumenal pH during dark-to-light transition compared to control strains. We conclude that BST4 is not a tethering protein but is most likely a pyrenoid tubule ion channel involved in the ion homeostasis of the lumen with particular importance during light fluctuations.

The intricate regulation of gene expression determining cell fate during male gametogenesis involves a complex interplay of multiple transcriptional regulators. In Arabidopsis (Arabidopsis thaliana), the LATERAL ORGAN BOUNDARIES DOMAIN 10 (LBD10) transcription factor is prominent in early microspores and both the germ and vegetative cells of bicellular pollen, playing an important role in pollen development. However, in mature pollen, LBD10 exclusively localizes in the vegetative cell nucleus. Here, we identify cis-acting elements and trans-acting factors responsible for the specific expression of LBD10 in the vegetative cell nucleus during pollen maturation. Using a series of LBD10 promoter deletion constructs fused with GUS or GFP reporters, we pinpoint two crucial core promoter sequences. These sequences are situated within two 200 bp regions upstream of the start codon and independently govern LBD10 expression in the vegetative cell nucleus. We demonstrate that a W-box motif (AGTCAC) at -770 bp is essential for activating the expression of LBD10 in vegetative cells during pollen maturation. Our transient gene expression assays using Arabidopsis protoplasts and chromatin immunoprecipitation assays show that the transcription factors WRKY2 and WRKY34 recognize the LBD10 promoter region containing W-box motifs. Collectively, our findings suggest that WRKY2 and WRKY34 binding to the W-box motifs plays a role in the vegetative cell nucleus-specific expression of LBD10 in pollen. This interaction may contribute to male gametophyte development, shedding light on the intricate regulatory network governing this critical biological process.

The 20-24 nucleotide microRNAs (miRNAs) and their target transcription factors (TF) have emerged as key regulators of diverse processes in plants, including organ development and environmental resilience. In several instances, the mature miRNAs degrade the TF-encoding transcripts, while their protein products in turn bind to the promoters of the respective miRNA-encoding genes and regulate their expression, thus forming feedback loops (FBLs) or feedforward loops (FFLs). Computational analysis suggested that such miRNA-TF loops are recurrent motifs in gene regulatory networks (GRNs) in plants as well as animals. In recent years, modeling and experimental studies have suggested that plant miRNA-TF loops in GRNs play critical roles in driving organ development and abiotic stress responses. Here, we discuss the miRNA-TF FBLs and FFLs that have been identified and studied in plants over the past decade. We then provide some insights into the possible roles of such motifs within GRNs. Lastly, we provide perspectives on future directions for dissecting the functions of miRNA-centric GRNs in plants.

The mirid bug (Riptortus pedestris), a major soybean pest, migrates into soybean fields during the pod filling stage and causes staygreen syndrome, which leads to substantial yield losses. The mechanism by which R. pedestris elicits soybean (Glycine max) defenses and counter-defenses remains largely unexplored. In this study, we characterized a protein family from R. pedestris, designated Riptortus pedestris HAMP 1 (RPH1) and its putative paralogs (RPH1L1, 2, 3, 4, and 5), whose members exhibit dual roles in triggering and inhibiting plant immunity. RPH1 and RPH1L1 function as herbivore-associated molecular patterns (HAMPs), activating pattern-triggered immunity (PTI) in tobacco (Nicotiana benthamiana) and G. max. Furthermore, RPH1 stimulates jasmonic acid and ethylene biosynthesis in G. max, thereby enhancing its resistance to R. pedestris feeding. Additionally, RPH1 homologs are universally conserved across various herbivorous species, with many homologs also acting as HAMPs that trigger plant immunity. Interestingly, the remaining RPH1 putative paralogs (RPH1L2-5) serve as effectors that counteract RPH1-induced PTI, likely by disrupting the extracellular perception of RPH1. This research uncovers a HAMP whose homologs are conserved in both chewing and piercing-sucking insects. Moreover, it unveils an extracellular evasion mechanism utilized by herbivores to circumvent plant immunity using functionally differentiated paralogs.

Breeding dwarf apple (Malus domestica) varieties is a recent trend in agriculture because such varieties are easy to maintain and have high yields; however, dwarf apple trees generally have poor stress tolerance. Balancing apple plant height and stress response has been an important breeding goal. In this study, aux/indole-3-acetic acid 29 gene in apple (MdIAA29) overexpression lines (#1, #2, #3) had reduced plant height by 39%, 31%, and 35%, respectively, suitable for close planting applications. Surprisingly, the dwarf MdIAA29-overexpression lines also showed increased plant tolerance to salt and drought stresses. Further analysis showed that MdIAA29 inhibited the regulation of auxin response factor 4 (ARF4) on Gretchen Hagen 3.9 (GH3.9) gene and 9-cis-epoxycarotenoid dioxygenase 3 (NCED3) gene in apple and changed the contents of auxin and abscisic acid in different tissues, thus achieving a balance between plant height and stress tolerance. In addition, we also found that MdIAA7 enhanced the inhibitory effect of MdIAA29 on MdARF4. In brief, the MdIAA29-MdARF4 complex significantly impacts the height of apple plants and their ability to respond to salt and drought stress.