Male sterility caused by long-term high-temperature (HT) stress occurs widely in crops. MicroRNAs (miRNAs), a class of endogenous non-coding small RNAs, play an important role in the plant response to various abiotic stresses. To dissect the working principle of miRNAs in male sterility under HT stress in cotton, a total of 112 known miRNAs, 270 novel miRNAs and 347 target genes were identified from anthers of HT-insensitive (84021) and HT-sensitive (H05) cotton cultivars under normal-temperature and HT conditions through small RNA and degradome sequencing. Quantitative reverse transcriptase-polymerase chain reaction and 5'-RNA ligase-mediated rapid amplification of cDNA ends experiments were used to validate the sequencing data. The results show that miR156 was suppressed by HT stress in both 84021 and H05; miR160 was suppressed in 84021 but induced in H05. Correspondingly, SPLs (target genes of miR156) were induced both in 84021 and H05; ARF10 and ARF17 (target genes of miR160) were induced in 84021 but suppressed in H05. Overexpressing miR160 increased cotton sensitivity to HT stress seen as anther indehiscence, associated with the suppression of ARF10 and ARF17 expression, thereby activating the auxin response that leads to anther indehiscence. Supporting this role for auxin, exogenous Indole-3-acetic acid (IAA) leads to a stronger male sterility phenotype both in 84021 and H05 under HT stress. Cotton plants overexpressing miR157 suppressed the auxin signal, and also showed enhanced sensitivity to HT stress, with microspore abortion and anther indehiscence. Thus, we propose that the auxin signal, mediated by miRNAs, is essential for cotton anther fertility under HT stress.

High-temperature (HT) stress induces male sterility, leading to yield reductions in crops. DNA methylation regulates a range of processes involved in plant development and stress responses, but its role in male sterility under HT remains unknown. Here, we investigated DNA methylation levels in cotton () anthers under HT and normal temperature (NT) conditions by performing whole-genome bisulfite sequencing to investigate the regulatory roles of DNA methylation in male fertility under HT. Global disruption of DNA methylation, especially CHH methylation (where H = A, C, or T), was detected in an HT-sensitive line. Changes in the levels of 24-nucleotide small-interfering RNAs were significantly associated with DNA methylation levels. Experimental suppression of DNA methylation led to pollen sterility in the HT-sensitive line under NT conditions but did not affect the normal dehiscence of anther walls. Further transcriptome analysis showed that the expression of genes in sugar and reactive oxygen species (ROS) metabolic pathways were significantly modulated in anthers under HT, but auxin biosynthesis and signaling pathways were only slightly altered, indicating that HT disturbs sugar and ROS metabolism via disrupting DNA methylation, leading to microspore sterility. This study opens up a pathway for creating HT-tolerant cultivars using epigenetic techniques.

Iontronic pressure sensors are promising in robot haptics because they can achieve high sensing performance using nanoscale electric double layers (EDLs) for capacitive signal output. However, it is challenging to achieve both high sensitivity and high mechanical stability in these devices. Iontronic sensors need microstructures that offer subtly changeable EDL interfaces to boost sensitivity, while the microstructured interfaces are mechanically weak. Here, we embed isolated microstructured ionic gel (IMIG) in a hole array (28 × 28) of elastomeric matrix and cross-link the IMIGs laterally to achieve enhanced interfacial robustness without sacrificing sensitivity. The embedded configuration toughens and strengthens the skin by pinning cracks and by the elastic dissipation of the interhole structures. Furthermore, cross-talk between the sensing elements is suppressed by isolating the ionic materials and by designing a circuit with a compensation algorithm. We have demonstrated that the skin is potentially useful for robotic manipulation tasks and object recognition.

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 Global warming has reduced the productivity of many field-grown crops due to effects on male sterility. The genetic regulation of high temperature (HT) response in the major crop cotton is poorly understood.  We determined the functionality and transcriptomes of anther of 218 cotton accessions grown under HT stress. By analyzing transcriptome divergence and implementing genome-wide association study (GWAS), we identified three thermal tolerance associated loci which contained 75 protein coding genes and 27 long non-coding RNAs, and provided expression quantitative trait loci (eQTLs) for 13,132 transcripts.  A transcriptome-wide association study (TWAS) confirmed six causal elements for the HT response (three genes overlapped with GWAS results), involved in protein kinase activity. The most susceptible gene, GhHRK1 was confirmed as a previously uncharacterized negative regulator of the HT response both in cotton and in Arabidopsis.  These functional variants provided new understanding of genetic basis for HT tolerance in male reproduction organs.

Abstract High temperature (HT) stress is an inevitable environmental factor in certain geographical regions. To study the effect of day/night HT stress on male reproduction development, the H05, a heat-sensitive cotton line, was subjected to HT stress. High day and Normal night (HN) and Normal day and High night (NH) temperature treatments were compared with control (Normal day and Normal night, NN). At the anther dehiscence stage, significant differences were found, with a reduction in flower size, filament length and sterility in pollen seen in NH more than in HN. A total of 36,806 differentially expressed genes were screened, which were mainly associated with fatty acid and jasmonic acid (JA) metabolic pathways. Fatty acid and JA contents reduced more in NH than HN. Under NH, ACYL-COA OXIDASE 2 (ACO2), a JA biosynthesis gene, was down-regulated as determined by qRT-PCR. Interestingly, the ACO2 CRISPR-Cas9 mutants show male-sterility under NN condition. Exogenous application of methyl jasmonate on early stage buds of mutants restored the sterile pollen and indehiscence anther phenotypes at late stage. These data showed that night HT might affect fatty acid and JA metabolism in anthers by suppressing GhACO2 and generate male sterility strongly than does high day temperature.

Annexins (Ann) are a multigene, evolutionarily conserved family of calcium-dependent and phospholipid-binding proteins that play important roles in plant development and stress resistance. However, a systematic comprehensive analysis of ANN genes of Brassicaceae species (Brassica rapa, Brassica oleracea, and Brassica napus) has not yet been reported. In this study, we identified 13, 12, and 26 ANN genes in B. rapa, B. oleracea, and B. napus, respectively. About half of these genes were clustered on various chromosomes. Molecular evolutionary analysis showed that the ANN genes were highly conserved in Brassicaceae species. Transcriptome analysis showed that different group ANN members exhibited varied expression patterns in different tissues and under different (abiotic stress and hormones) treatments. Meanwhile, same group members from Arabidopsis thaliana, B. rapa, B. oleracea, and B. napus demonstrated conserved expression patterns in different tissues. The weighted gene coexpression network analysis (WGcnA) showed that BnaANN genes were induced by methyl jasmonate (MeJA) treatment and played important roles in jasmonate (JA) signaling and multiple stress response in B. napus.Annexins (ANN) are a multigene, evolutionarily conserved family of calcium (Ca 2+ )-dependent and phospholipid-binding proteins present in plants, animals, and microorganisms 1,2 . ANN contain the characteristic annexin repeat and they regulate membrane dynamics, mediate Ca 2+ sensing and signaling, link Ca 2+ dynamics to cytoskeletal responses, and mediate immune or stress responses and signaling during plant growth and development 1,3 . A typical ANN contains four annexin repeats at the C-terminal region and a highly variable N-terminal region. Each annexin repeat usually contains a characteristic type II motif for Ca 2+ binding 1,3 . The variable N-terminal region interacts with other proteins and is responsible for the functional diversity of ANN 4 .Recent studies have identified the ANN gene family in Arabidopsis thaliana (8 genes), Brassica rapa (13), Solanum lycopersicum (9), Solanum tuberosum (9), Oryza sativa (10), Triticum aestivum (25), Gossypium raimondii (14), Arachis hypogaea L. (8), Hordeum vulgare (11), Medicago truncatula (10), Populus trichocarpa (12), Vitis vinifera (14), Carica papaya (12), Glycine max (22), Cochliobolus sativus (11), Sorghum bicolor (10), Zea mays (12), Brachypodium distachyon (11), Selaginella mollendorffii (5), and Physcomitrella patens (7) via genome-wide analysis 2,5-11 .Studies have shown that ANN gene family plays a significant role in plant development and plant protection during both abiotic and biotic stresses 1,3,12,13 . In Arabidopsis, two ANN genes (AtANN1 and AtANN4) were regulated by abiotic stress, negatively regulated plant tolerance to drought, salinity, and heat stress, while AtANN8 was open Scientific RepoRtS | (2020) 10:4295 | https://doi.org/10.1038/s41598-020-59953-w www.nature.com/scientificreports www.nature.com/scientificreports/ positive regulated the plant abiotic tolerance [...

Summary The pollen wall exine provides a protective layer for the male gametophyte and is largely composed of sporopollenin, which comprises fatty acid derivatives and phenolics. However, the biochemical nature of the external exine is poorly understood. Here, we show that the male sterile line 1355A of cotton mutated in NO SPINE POLLEN (GhNSP) leads to defective exine formation. The GhNSP locus was identified through map‐based cloning and confirmed by genetic analysis (co‐segregation test and allele prediction using the CRISPR/Cas9 system). In situ hybridization showed that GhNSP is highly expressed in tapetum. GhNSP encodes a polygalacturonase protein homologous to AtQRT3, which suggests a function for polygalacturonase in pollen exine formation. These results indicate that GhNSP is functionally different from AtQRT3, the latter has the function of microspore separation. Biochemical analysis showed that the percentage of de‐esterified pectin was significantly increased in the 1355A anthers at developmental stage 8. Furthermore, immunofluorescence studies using antibodies to the de‐esterified and esterified homogalacturonan (JIM5 and JIM7) showed that the Ghnsp mutant exhibits abundant of de‐esterified homogalacturonan in the tapetum and exine, coupled with defective exine formation. The characterization of GhNSP provides new understanding of the role of polygalacturonase and de‐esterified homogalacturonan in pollen exine formation.