FLS2-RBOHD-PIF4 Module Regulates Plant Response to Drought and Salt Stress.

As sessile organisms, plants are constantly challenged by several environmental stresses. Different kinds of stress often occur simultaneously, leading to the accumulation of reactive oxygen species (ROS) produced by respiratory burst oxidase homolog (RBOHD) and calcium fluctuation in cells. Extensive studies have revealed that flagellin sensitive 2 (FLS2) can sense the infection by pathogenic microorganisms and activate cellular immune response by regulating intracellular ROS and calcium signals, which can also be activated during plant response to abiotic stress. However, little is known about the roles of FLS2 and RBOHD in regulating abiotic stress. In this study, we found that although the fls2 mutant showed tolerance, the double mutant rbohd rbohf displayed hypersensitivity to abiotic stress, similar to its performance in response to immune stress. An analysis of the transcriptome of the fls2 mutant and rbohd rbohf double mutant revealed that phytochrome interacting factor 4 (PIF4) acted downstream of FLS2 and RBOHD to respond to the abiotic stress. Further analysis showed that both FLS2 and RBOHD regulated the response of plants to drought and salt stress by regulating the expression of PIF4. These findings revealed an FLS2-RBOHD-PIF4 module in regulating plant response to biotic and abiotic stresses.

Global Dynamic Molecular Profiling of Stomatal Lineage Cell Development by Single-Cell RNA Sequencing.

The regulation of stomatal lineage cell development has been extensively investigated. However, a comprehensive characterization of this biological process based on single-cell transcriptome analysis has not yet been reported. In this study, we performed RNA sequencing on 12 844 individual cells from the cotyledons of 5-day-old Arabidopsis seedlings. We identified 11 cell clusters corresponding mostly to cells at specific stomatal developmental stages using a series of marker genes. Comparative analysis of genes with the highest variable expression among these cell clusters revealed transcriptional networks that regulate development from meristemoid mother cells to guard mother cells. Examination of the developmental dynamics of marker genes via pseudo-time analysis revealed potential interactions between these genes. Collectively, our study opens the door for understanding how the identified novel marker genes participate in the regulation of stomatal lineage cell development.

WRKY33-PIF4 loop is required for the regulation of H2O2 homeostasis.

The reactive oxygen species (ROS) are continuously produced and are essential for mediating the growth and development of plants. However too much accumulation of ROS can result in the oxidative damage to cells, especially under the adverse environmental conditions. Plants have evolved sophisticated strategies to regulate the homeostasis of H2O2. In this study, we generated transgenic Arabidopsis plants in the Ws ecotype (Ws) background in which WRKY33 is co-suppressed (csWRKY33/Ws). Compared with Ws, csWRKY33/Ws plants accumulate more H2O2. RNA-seq analysis indicated that in csWRKY33/Ws plants, expression of oxidative stress related genes such as ascorbate peroxidase 2 (APX2) is affected. Over-expression of APX2 can rescue the phenotype of csWRKY33/Ws, suggesting that the changes in the growth of csWRKY33/Ws is duo to the higher accumulation of H2O2. Analysis of the CHIP-seq data suggested that WRKY33 can directly regulate the expression of PIF4, vice versa. qPCR analysis also confirmed that the mutual regulation between WRKY33 and PIF4. Similar to that of csWRKY33/Ws, and the accumulation of H2O2 in pif4 also increased. Taken together, our results reveal a WRKY33-PIF4 regulatory loop that appears to play an important role in regulating the growth and development of seedlings by mediating H2O2 homeostasis.

COE 1 and GUN1 regulate the adaptation of plants to high light stress.

In order to withstand high light (HL) stress, plants have evolved both short-term defense and repair mechanisms and long-term acclimation responses. At present, however, the underlying signaling events and molecular mechanisms are still poorly understood. Analysis of the mutants coe1, coe1 gun1 double mutant and oeGUN1coe1 revealed increased sensitivity to HL stress as compared to wild type (WT), with oeGUN1 coe1 plants displaying the highest sensitivity. Accumulation of FTSH2 protein and degradation of D1 protein during the HL stress were shown to depend on both COE1 and GUN1. Overexpression of COE1 enhanced the induction of FTSH2 and the tolerance to HL stress. These results indicate that the COE1-GUN1 signaling pathway plays an important role in regulating the adaptation of plants to HL.

Profiling of the Receptor for Activated C Kinase 1a (RACK1a) interaction network in Arabidopsis thaliana.

As a scaffold protein, Receptor for Activated C Kinase 1a (RACK1) interacts with many proteins and is involved in multiple biological processes in Arabidopsis. However, the global RACK1 protein interaction network in higher plants remains poorly understood. Here, we generated a yeast two-hybrid library using mixed samples from different developmental stages of Arabidopsis thaliana. Using RACK1a as bait, we performed a comprehensive screening of the resulting library to identify RACK1a interactors at the whole-transcriptome level. We selected 1065 independent positive clones that led to the identification of 215 RACK1a interactors. We classified these interactors into six groups according to their potential functions. Several interactors were selected for bimolecular fluorescence complementation (BiFC) analysis and their interaction with RACK1a was confirmed in vivo. Our results provide further insight into the molecular mechanisms through which RACK1a regulates various growth and development processes in higher plants.