Regulatory hubs in plant stress adaptation

Molecular insights into OPR gene family in Saccharum identified a ScOPR2 gene could enhance plant disease resistance

12-Oxo-phytodienoic acid reductases (OPRs) perform vital functions in plants. However, few studies have been reported in sugarcane (Saccharum spp.), and it is of great significance to systematically investigates it in sugarcane. Here, 61 ShOPRs, 32 SsOPRs, and 36 SoOPRs were identified from R570 (Saccharum spp. hybrid cultivar R570), AP85-441 (Saccharum spontaneum), and LA-purple (Saccharum officinarum), respectively. These OPRs were phylogenetically classified into four groups, with close genes similar structures. During evolution, OPR gene family was mainly expanded via whole-genome duplications/segmental events and predominantly underwent purifying selection, while sugarcane OPR genes may function differently in response to various stresses. Further, ScOPR2, a tissue-specific OPR, which was localized in cytoplasm and cell membrane and actively response to salicylic acid (SA), methyl jasmonate, and smut pathogen (Sporisorium scitamineum) stresses, was cloned from sugarcane. In addition, both its transient overexpression and stable overexpression enhanced the resistance of transgenic plants to pathogen infection, most probably through activating pathogen-associated molecular pattern/pattern-recognition receptor-triggered immunity, producing reactive oxygen species, and initiating mitogen-activated protein kinase cascade. Subsequently, the transmission of SA and hypersensitive reaction were triggered, which stimulated the transcription of defense-related genes. These findings provide insights into the function of ScOPR2 gene for disease resistance.

Morpho-physiological adaptations to weed competition impair green bean (Phaseolus vulgaris) ability to overcome moderate salt stress

The two stresses of weed competition and salt salinity lead to crop yield losses and decline in the productivity of agricultural land. These constraints threaten the future of food production because weeds are more salt stress tolerant than most crops. Climate change will lead to an increase of soil salinity worldwide, and possibly exacerbate the competition between weeds and crops. This aspect has been scarcely investigated in the context of weed-crop competition. Therefore, we conducted a field experiment on green beans (Phaseolus vulgaris ) to investigate the combined impact of weed competition and salt stress on key morpho-physiological traits, and crop yield. We demonstrated that soil salinity shifted weed composition toward salt tolerant weed species (Portulaca oleracea and Cynodon dactylon ), while it reduced the presence of lower tolerance species. Weed competition activated adaptation responses in green bean such as reduced leaf mass per area and biomass allocation to the stem, unchanged stomatal density and instantaneous water use efficiency, which diverge from those that are typically observed as a consequence of salt stress. The morpho-physiological modifications caused by weeds is attributed to the alterations of light intensity and/or quality, further confirming the pivotal role of the light in crop response to weeds. We concluded that higher yield loss caused by combined salt stress and weed competition is due to impaired morpho-physiological responses, which highlights the negative interaction between salt stress and weed competition. This phenomenon will likely be more frequent in the future, and potentially reduce the efficacy of current weed control methods.

Identification and Expression Profiling of WRKY Family Genes in Sugarcane in Response to Bacterial Pathogen Infection and Nitrogen Implantation Dosage

WRKY transcription factors (TFs) are essential players in different signaling cascades and regulatory networks involved in defense responses to various stressors. This study systematically analyzed and characterized WRKY family genes in the Saccharum spp. hybrid R570 and their expression in two sugarcane cultivars LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald) in response to bacterial pathogen infection and nitrogen implantation dosage. A total of 53 ShWRKY genes with 66 alleles were systematically identified in R570 based on the query sequence SsWRKY in S. spontaneum AP85-441. All ShRWKY alleles were further classified into four groups with 11 (16.7%) genes in group I, 36 (54.5%) genes in group II, 18 (27.3%) genes in group III, and 1 (1.5%) gene in group IV. Among them, 4 and 11 ShWRKY gene pairs displayed tandem and segmental duplication events, respectively. The ShWRKY genes exhibited conserved DNA-binding domains, which were accompanied by variations in introns, exons, and motifs. RT-qPCR analysis of two sugarcane cultivars triggered by Xanthomonas albilineans (Xa) revealed that four genes, ShWRKY13-2/39-1/49-3/125-3, exhibited significant upregulation in leaf scald-resistant LCP85-384. These WRKY genes were downregulated or unchanged in ROC20 at 24-72 h post-inoculation, suggesting that they play an important role in defense responses to Xa infection. Most of the 12 tested ShWRKYs, ShWRKY22-1/49-3/52-1 in particular, functioned as negative regulators in the two cultivars in response to a range of nitrogen (N) implantation doses. A total of 11 ShWRKY proteins were predicted to interact with each other. ShWRKY43 and ShWRKY49-3 are predicted to play core roles in the interaction network, as indicated by their interaction with six other ShWRKY proteins. Our results provide important candidate gene resources for the genetic improvement of sugarcane and lay the foundation for further functional characterization of ShWRKY genes in response to coupling effects of Xa infection and different N levels.