These authors contributed equally to this work. SUMMARYAuxin and cadmium (Cd) stress play critical roles during root development. There are only a few reports on the mechanisms by which Cd stress influences auxin homeostasis and affects primary root (PR) and lateral root (LR) development, and almost nothing is known about how auxin and Cd interfere with root hair (RH) development. Here, we characterize rice osaux1 mutants that have a longer PR and shorter RHs in hydroponic culture, and that are more sensitive to Cd stress compared to wild-type (Dongjin). OsAUX1 expression in root hair cells is different from that of its paralogous gene, AtAUX1, which is expressed in non-hair cells. However, OsAUX1, like AtAUX1, localizes at the plasma membrane and appears to function as an auxin tranporter. Decreased auxin distribution and contents in the osaux1 mutant result in reduction of OsCyCB1;1 expression and shortened PRs, LRs and RHs under Cd stress, but may be rescued by treatment with the membrane-permeable auxin 1-naphthalene acetic acid. Treatment with the auxin transport inhibitors 1-naphthoxyacetic acid and N-1-naphthylphthalamic acid increased the Cd sensitivity of WT rice. Cd contents in the osaux1 mutant were not altered, but reactive oxygen species-mediated damage was enhanced, further increasing the sensitivity of the osaux1 mutant to Cd stress. Taken together, our results indicate that OsAUX1 plays an important role in root development and in responses to Cd stress.

SummaryPhosphorus (P) is crucial nutrient element for crop growth and development. However, the network pathway regulating homeostasis of phosphate (Pi) in crops has many molecular breeding unknowns. Here, we report that an auxin response factor, OsARF12, functions in Pi homeostasis.Measurement of element content, quantitative reverse transcription polymerase chain reaction analysis and acid phosphatases (APases) activity assay showed that the osarf12 mutant and osarf12/25 double mutant with P-intoxicated phenotypes had higher P concentrations, up-regulation of the Pi transporter encoding genes and increased APase activity under Pi-sufficient/-deficient (+Pi/ÀPi, 0.32/0 mM NaH 2 PO 4 ) conditions.Transcript analysis revealed that Pi-responsive genes -Phosphate starvation (OsIPS)1 and OsIPS2, SYG1/Pho81/XPR1(OsSPX1), Sulfoquinovosyldiacylglycerol 2 (OsSQD2), R2R3 MYB transcription factor (OsMYB2P-1) and Transport Inhibitor Response1 (OsTIR1) -were more abundant in the osarf12 and osarf12/25 mutants under +Pi/ÀPi conditions. Knockout of OsARF12 also influenced the transcript abundances of the OsPHR2 gene and its downstream components, such as OsMiR399j, OsPHO2, OsMiR827, OsSPX-MFS1 and OsSPX-MFS2. Results from -Pi/1-naphthylphthalamic acid (NPA) treatments, and auxin reporter DR5::GUS staining suggest that root system alteration and Pi-induced auxin response were at least partially controlled by OsARF12.These findings enrich our understanding of the biological functions of OsARF12, which also acts in regulating Pi homeostasis.

In rice, there are five members of the auxin carrier AUXIN1/LIKE AUX1 family; however, the biological functions of the other four members besides OsAUX1 remain unknown. Here, by using CRISPR/Cas9, we constructed two independent OsAUX3 knock‐down lines, osaux3‐1 and osaux3‐2, in wild‐type rice, Hwayoung (WT/HY) and Dongjin (WT/DJ). osaux3‐1 and osaux3‐2 have shorter primary roots (PRs), decreased lateral root (LR) density, and longer root hairs (RHs) compared with their WT. OsAUX3 expression in PRs, LRs, and RHs further supports that OsAUX3 plays a critical role in the regulation of root development. OsAUX3 locates at the plasma membrane and functions as an auxin influx carrier affecting acropetal auxin transport. OsAUX3 is up‐regulated in the root apex under aluminium (Al) stress, and osaux3‐2 is insensitive to Al treatments. Furthermore, 1‐naphthylacetic acid accented the sensitivity of WT/DJ and osaux3‐2 to respond to Al stress. Auxin concentrations, Al contents, and Al‐induced reactive oxygen species‐mediated damage in osaux3‐2 under Al stress are lower than in WT, indicating that OsAUX3 is involved in Al‐induced inhibition of root growth. This study uncovers a novel pathway alleviating Al‐induced oxidative damage by inhibition of acropetal auxin transport and provides a new option for engineering Al‐tolerant rice species.

Background Salinization seriously threatens land use efficiency and crop yields across the world. Understanding the mechanisms plants use to protect against salt stress will help breeders develop salt-tolerant vegetable crops. Okra ( Abelmoschus esculentus L.) is an important vegetable crop of the mallow family, which is now cultivated in warm regions worldwide. To understand the effects of salt stress on the protein level of okra, a comparative proteomic analysis of okra seedlings grown in the presence of 0 or 300 mmol L − 1 NaCl treatment was performed using an integrated approach of Tandem Mass Tag labeling and LC-MS/MS integrated approach. Results A total of 7179 proteins were identified in this study, for which quantitative information was available for 5774 proteins. In the NaCl/control comparison group, there were 317 differentially expressed proteins (DEPs), of which 165 proteins were upregulated and 152 proteins downregulated in the presence of NaCl. Based on the above data, we carried out a systematic bioinformatics analysis of proteins with information, including protein annotation, domain characteristics, functional classification, and pathway enrichment. Enriched gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the DEPs were most strongly associated with “response to stress” and “protein processing in endoplasmic reticulum”. Furthermore, several heat shock proteins were identified as DEPs. Conclusions This information provides a reference direction for further research on the okra proteome in the downstream of the salt stress response, with our data revealing that the responses of okra to salt stress involves by various pathways. Electronic supplementary material The online version of this article (10.1186/s12864-019-5737-7) contains supplementary material, which is available to authorized users.

Auxin response factors (ARFs) play important roles in regulating plant growth and development and response to environmental stress. An exhaustive analysis of the CaARF family was performed using the latest publicly available genome for pepper (Capsicum annuum L.). In total, 22 non-redundant CaARF gene family members in six classes were analyzed, including chromosome locations, gene structures, conserved motifs of proteins, phylogenetic relationships and Subcellular localization. Phylogenetic analysis of the ARFs from pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), Arabidopsis and rice (Oryza sativa L.) revealed both similarity and divergence between the four ARF families, and aided in predicting biological functions of the CaARFs. Furthermore, expression profiling of CaARFs was obtained in various organs and tissues using quantitative real-time RT-PCR (qRT-PCR). Expression analysis of these genes was also conducted with various hormones and abiotic treatments using qRT-PCR. Most CaARF genes were regulated by exogenous hormone treatments at the transcriptional level, and many CaARF genes were altered by abiotic stress. Systematic analysis of CaARF genes is imperative to elucidate the roles of CaARF family members in mediating auxin signaling in the adaptation of pepper to a challenging environment.

The regulator of chromosome condensation 1 (RCC1) is the nucleotide exchange factor for a GTPase called the Ras-related nuclear protein, and it is important for nucleo-plasmic transport, mitosis, nuclear membrane assembly, and control of chromatin agglutination during the S phase of mitosis in animals. In plants, RCC1 molecules act mainly as regulating factors for a series of downstream genes during biological processes such as the ultraviolet-B radiation (UV-B) response and cold tolerance. In this study, 56 genes were identified in upland cotton by searching the associated reference genomes. The genes were found to be unevenly distributed on 26 chromosomes, except A06, A12, D03, and D12. Phylogenetic analysis by maximum-likelihood revealed that the genes were divided into five subgroups. The RCC1 genes within the same group shared similar exon/intron patterns and conserved motifs in their encoded proteins. Most genes of the RCC1 family are expressed differently under various hormone treatments and are negatively controlled by salt stress. Gh_A05G3028 and Gh_D10G2310, which encode two proteins located in the nucleus, were strongly induced under salt treatment, while mutants of their homoeologous gene (UVR8) in Arabidopsis and VIGS (virus induced gene silencing) lines of the two genes above in G. hirsutum exhibited a salt-sensitive phenotype indicating their potential role in salt resistance in cotton. These results provide valuable reference data for further study of RCC1 genes in cotton.

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Saline stress is a significant factor that caused crop growth inhibition and yield decline. SHORT INTERNODES/STYLISH (SHI/STY) and SHI-RELATED SEQUENCE (SRS) transcription factors are specific to plants and share a conserved RING-like zinc-finger domain (CX2CX7CX4CX2C2X6C). However, the functions of SHI/STY and SRS genes in cotton responses to salt stress remain unclear. In this study, 26 GhSRSs were identified in Gossypium hirsutum, which further divided into three subgroups. Phylogenetic analysis of 88 SRSs from8 plant species revealed independent evolutionary pattern in some of SRSs derived from monocots. Conserved domain and subcellular location predication of GhSRSs suggested all of them only contained the conserved RING-like zinc-finger domain (DUF702) domain and belonged to nucleus-localized transcription factors except for the GhSRS22. Furthermore, synteny analysis showed structural variation on chromosomes during the process of cotton polyploidization. Subsequently, expression patterns of GhSRS family members in response to salt and drought stress were analyzed in G. hirsutum and identified a salt stress-inducible gene GhSRS21. The GhSRS21 was proved to localize in the nuclear and silencing it in G. hirsutum increased the cotton resistance to salt using the virus-induced gene silencing (VIGS) system. Finally, our transcriptomic data revealed that GhSRS21 negatively controlled cotton salt tolerance by regulating the balance between ROS production and scavenging. These results will increase our understanding of the SRS gene family in cotton and provide the candidate resistant gene for cotton breeding.