Summary
Cleistogenes songorica (2n = 4x = 40) is a desert grass with a unique dimorphic flowering mechanism and an ability to survive extreme drought. Little is known about the genetics underlying drought tolerance and its reproductive adaptability. Here, we sequenced and assembled a high‐quality chromosome‐level C. songorica genome (contig N50 = 21.28 Mb). Complete assemblies of all telomeres, and of ten chromosomes were derived. C. songorica underwent a recent tetraploidization (~19 million years ago) and four major chromosomal rearrangements. Expanded genes were significantly enriched in fatty acid elongation, phenylpropanoid biosynthesis, starch and sucrose metabolism, and circadian rhythm pathways. By comparative transcriptomic analysis we found that conserved drought tolerance related genes were expanded. Transcription of CsMYB genes was associated with differential development of chasmogamous and cleistogamous flowers, as well as drought tolerance. Furthermore, we found that regulation modules encompassing miRNA, transcription factors and target genes are involved in dimorphic flower development, validated by overexpression of CsAP2_9 and its targeted miR172 in rice. Our findings enable further understanding of the mechanisms of drought tolerance and flowering in C. songorica, and provide new insights into the adaptability of native grass species in evolution, along with potential resources for trait improvement in agronomically important species.
We studied the genome-wide multiple time-course transcriptome dynamics after saliva deposition in alfalfa and demonstrate that saliva deposition functions as a stress that negatively affects the regrowth of alfalfa. Saliva deposition is one of the key factors influencing plant-herbivore interactions during grazing. Although many studies have focused on the effects of saliva deposition on plant regrowth, no consistent conclusions have been reached. Alfalfa is the most extensively cultivated forage legume, yet most alfalfa cultivars, thus far, are not grazing-tolerant. To better understand the underlying mechanism, we undertook a study to evaluate the global changes in the transcriptome of alfalfa after cow saliva deposition treatment. In this study, cDNA libraries from alfalfa seedlings at 0, 4, 8, and 24 h after cow saliva deposition were constructed and sequenced, resulting in the identification of 53,195 annotated unigenes, from which 4,814 unigenes were significantly differentially expressed. A metabolic pathway enrichment analysis demonstrated that saliva deposition functions as a stress that negatively affects the regrowth of alfalfa by modifying jasmonic acid synthesis, enhancing the susceptibility to pathogens and reducing the expression levels of ribosomal protein genes. In the present study, we demonstrate the potential effects of saliva deposition on alfalfa regrowth at the transcriptome level. These fundamental and important findings could facilitate further investigations into the molecular mechanisms underlying the responses of alfalfa and other related species to herbivore grazing.
Alfalfa is the most extensively cultivated forage legume, yet most alfalfa cultivars are not aluminum tolerant, and the molecular mechanisms underlying alfalfa responses to Al stress are largely unknown. In this study, we aimed to understand how alfalfa responds to Al stress by identifying and analyzing Al-stress-responsive genes in alfalfa roots at the whole-genome scale. The transcriptome changes in alfalfa roots under Al stress for 4, 8, or 24 h were analyzed using Illumina high-throughput sequencing platforms. A total of 2464 differentially expressed genes (DEGs) were identified, and most were up-regulated at early (4 h) and/or late (24 h) Al exposure time points rather than at the middle exposure time point (8 h). Metabolic pathway enrichment analysis demonstrated that the DEGs involved in ribosome, protein biosynthesis, and process, the citrate cycle, membrane transport, and hormonal regulation were preferentially enriched and regulated. Biosynthesis inhibition and signal transduction downstream of auxin- and ethylene-mediated signals occur during alfalfa responses to root growth inhibition. The internal Al detoxification mechanisms play important roles in alfalfa roots under Al stress. These findings provide valuable information for identifying and characterizing important components in the Al signaling network in alfalfa and enhance understanding of the molecular mechanisms underlying alfalfa responses to Al stress.
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