Plants are in a constant battle against different kinds of parasites throughout their life cycles (e.g., viruses, bacteria, fungi, oomycetes, insects, and parasitic plants). To maintain surveillance, plants have evolved complex but fine-tuned defence mechanisms (Jones & Dangl, 2006;Wu et al., 2018;Yuan et al., 2021). Small noncoding RNAs (sRNAs), as major modulators of gene expression, precisely regulate plant immunity. MicroRNAs (miRNAs) and small interfering RNAs (siRNA) are two major classes of plant sRNAs. miRNAs, in particular, have well-documented roles in regulating plant immunity, including switching plant growth and immunity, regulating immune signal transduction, and buffering transcript dosage of immune receptors (Qiao, Xia, et al., 2021;Song et al., 2021;Weiberg & Jin, 2015). siRNAs, on the other hand, are primarily known for their roles in silencing viral RNAs. However, recent discoveries of trans-species RNA interference (RNAi) have uncovered the essential role of siRNAs in repressing cellular pathogens. Emerging evidence supports a novel mode of action for plant endogenous sRNAs, particularly siRNAs, in repressing fungal and oomycete infection via the silencing of pathogen genes. These studies suggest that siRNAs, usually consisting of a mixture of diverse sequences, are deployed as a "shotgun" approach to target pathogen genes in a random, yet efficient manner. Many aspects of trans-species RNAi, however, remain

Auxin signalling plays a key role in various developmental processes ranging from embryogenesis to senescence in plants. Auxin response factor (ARF), a key component of auxin signalling, functions by binding to auxin response element within promoter of auxin response genes, activating or repressing the target genes. Increasing evidences show that ARFs are crucial for plant response to stresses. This review summarises the recent advance on the functions and their regulatory pathways of rice ARFs in development and responding to stresses. The importance of OsARFs is demonstrated by their roles in triggering various physiological, biochemical and molecular reactions to resist adverse environmental conditions. We also describe the transcriptional and post‐transcriptional regulation of OsARFs, and discuss the major challenges in this area.

Biodiversity in plant shape is mainly attributable to the diversity of leaf shape, which is largely determined by the transient morphogenetic activity of the leaf margin that creates leaf serrations. However, the precise mechanism underlying the establishment of this morphogenetic capacity remains poorly understood. We report here that INDOLE-3-BUTYRIC ACID RESPONSE 5 (IBR5), a dual-specificity phosphatase, is a key component of leaf-serration regulatory machinery. Loss-of-function mutants of IBR5 exhibited pronounced serrations due to increased cell area. IBR5 was localized in the nucleus of leaf epidermis and petiole cells. Introducing a C129S mutation within the highly conserved VxVHCx2GxSRSx5AYLM motif of IBR5 rendered it unable to rescue the leaf-serration defects of the ibr5-3 mutant. In addition, auxin reporters revealed that the distribution of auxin maxima was expanded ectopically in ibr5-3. Furthermore, we found that the distribution of PIN1 on the plasma membrane of the epidermal and cells around the leaf vein was compromised in ibr5-3. We concluded that IBR5 is essential for the establishment of PIN-FORMED 1 (PIN1)-directed auxin maxima at the tips of leaf serration, which is vital for the elaborated regulation during its formation.

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Plants exhibit remarkable developmental plasticity, enabling them to adapt to adverse environmental conditions such as low nitrogen (N) in the soil. Brassinosteroids (BRs) promote root foraging for nutrients under mild N deficiency, but the crosstalk between the BR- and N-signaling pathways in the regulation of root growth remains largely unknown. Here, we show that CALMODULIN-LIKE-38 (CML38), a calmodulin-like protein, specifically interacts with the PEP1 RECEPTOR 2 (PEPR2), and negatively regulates root elongation in Arabidopsis (Arabidopsis thaliana) in response to low nitrate. CML38 and PEPR2 are transcriptionally induced by treatments of exogenous nitrate and BR. Compared with Col-0, the single mutants cml38 and pepr2 and the double mutant cml38 pepr2 displayed enhanced primary root growth and produced more lateral roots (LRs) under low nitrate. This is consistent with their higher nitrate absorption abilities, and their stronger expression of nitrate assimilation genes. Furthermore, CML38 and PEPR2 regulate common downstream genes related to BR signaling, and they have positive roles in BR signaling. Low N facilitated BR signal transmission in Col-0 and CML38- or PEPR2-overexpressing plants, but not in the cml38 and pepr2 mutants. Taken together, our results illustrate a mechanism by which CML38 interacts with PEPR2 to integrate low-nitrate and BR signals for coordinating root development to prevent quick depletion of N resources in Arabidopsis.