Induction of jasmonic acid biosynthetic genes inhibits Arabidopsis growth in response to low boron

Physiological and transcriptomic analysis of tomato in response to sub-optimal temperature stress

Tomato (Solanum lycopersicum L.) is one of the most important economic crops in China. However, its quality and yield are susceptible to the adverse effects of low temperatures. In our study, two tomato cultivars, showing different tolerance to low temperatures, namely the cold-sensitive tomato cultivar (S708) and cold-tolerant tomato cultivar (T722), were grown at optimal (25/18°C) and sub-optimal (15/10°C) temperature conditions for 5 days. Our study aimed to explore the effect of sub-optimal temperature on fresh weight, chlorophyll content and chlorophyll fluorescence, soluble sugars and proline content of two tomato cultivars. Moreover, we employed RNA-Seq to analyze the transcriptomic response of tomato roots to sub-optimal temperature. The results revealed that S708 showed a more significant reduction in fresh weight, chlorophyll content, photochemical efficiency of PSII (YII), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qP) and electron transport rate (ETR) compared to T722 under the sub-optimal temperature condition. Notably, T722 maintained higher level of soluble sugars and proline in comparison to S708 uner sub-optimal temperature. RNA-seq data showed that up-regulated DEGs in both tomato cultivars were involved in "plant-pathogen interaction", "MAPK signaling pathway", "plant hormone signal transduction", and "phosphatidylinositol signaling system". Furthermore, "Amino sugar and nucleotide sugar metabolism" pathway was enriched only in T722. Moreover, under sub-optimal temperature, transcription factor genes and osmoregulation genes showed varying degrees of response in both tomato cultivars. Conclusion: In summary, our results offer detailed insights into the response characteristics of tomato to sub-optimal temperature, providing valuable references for the practical management of tomato crops under sub-optimal temperature condition.

Ascorbic acid treatment inhibits early wound healing in the fresh-cut potato by relegating jasmonic acid biosynthesis and signal transduction

Jasmonic acid (JA) is a wound hormone involved in plant defence responses. Ascorbic acid (AsA) treatment could inhibit early wound healing in fresh-cut potatoes (FCPs), but its regulation of JA pathway during this process remains unclear. We investigated the effects of AsA on JA biosynthesis and signal transduction in FCPs during wound healing. Results showed that AsA treatment decreased JA biosynthesis pathway-related enzyme activities and gene expression (StLOX3.1, StAOS1, StOPR1, StADH1, StKAT2, and StACOT13) at the wound site during healing. The JA content increased from 0.443 to 1.205 μg g-1 within 10 h but only increased to 0.535 μg g-1 with AsA. AsA treatment reduced jasmonic acid carboxyl methyltransferase and jasmonic acid-amido synthetase activities, StJMT and StJAR1 expressions, and methyl jasmonate and jasmonoyl-isoleucine contents. Moreover, AsA treatment upregulated StJAZ1 and downregulated StMYC2 expression. These findings suggested that AsA regulates wound healing in FCPs by suppressing JA biosynthesis and signal transduction.

Genome-Wide Identification of Sorghum Paclobutrazol-Resistance Gene Family and Functional Characterization of SbPRE4 in Response to Aphid Stress

Sorghum (Sorghum bicolor), the fifth most important cereal crop globally, serves as a staple food, animal feed, and a bioenergy source. Paclobutrazol-Resistance (PRE) genes play a pivotal role in the response to environmental stress, yet the understanding of their involvement in pest resistance remains limited. In the present study, a total of seven SbPRE genes were found within the sorghum BTx623 genome. Subsequently, their genomic location was studied, and they were distributed on four chromosomes. An analysis of cis-acting elements in SbPRE promoters revealed that various elements were associated with hormones and stress responses. Expression pattern analysis showed differentially tissue-specific expression profiles among SbPRE genes. The expression of some SbPRE genes can be induced by abiotic stress and aphid treatments. Furthermore, through phytohormones and transgenic analyses, we demonstrated that SbPRE4 improves sorghum resistance to aphids by accumulating jasmonic acids (JAs) in transgenic Arabidopsis, giving insights into the molecular and biological function of atypical basic helix-loop-helix (bHLH) transcription factors in sorghum pest resistance.

Linking the key physiological functions of essential micronutrients to their deficiency symptoms in plants

In this review, we untangle the physiological key functions of the essential micronutrients and link them to the deficiency responses in plants. Knowledge of these responses at the mechanistic level, and the resulting deficiency symptoms, have improved over the last decade and it appears timely to review recent insights for each of them. A proper understanding of the links between function and symptom is indispensable for an accurate and timely identification of nutritional disorders, thereby informing the design and development of sustainable fertilization strategies. Similarly, improved knowledge of the molecular and physiological functions of micronutrients will be important for breeding programmes aiming to develop new crop genotypes with improved nutrient-use efficiency and resilience in the face of changing soil and climate conditions.

Understanding the role of boron in plant adaptation to soil salinity

Soil salinity is a major environmental constraint affecting the sustainability and profitability of agricultural production systems. Salinity stress tolerance has been present in wild crop relatives but then lost, or significantly weakened, during their domestication. Given the genetic and physiological complexity of salinity tolerance traits, agronomical solutions may be a suitable alternative to crop breeding for improved salinity stress tolerance. One of them is optimizing fertilization practices to assist plants in dealing with elevated salt levels in the soil. In this review, we analyse the causal relationship between the availability of boron (an essential metalloid micronutrient) and plant's adaptive responses to salinity stress at the whole-plant, cellular, and molecular levels, and a possibility of using boron for salt stress mitigation. The topics covered include the impact of salinity and the role of boron in cell wall remodelling, plasma membrane integrity, hormonal signalling, and operation of various membrane transporters mediating plant ionic and water homeostasis. Of specific interest is the role of boron in the regulation of H+-ATPase activity whose operation is essential for the control of a broad range of voltage-gated ion channels. The complex relationship between boron availability and expression patterns and the operation of aquaporins is also discussed.

Boron homeostasis affects Longan yield: a study of NIP and BOR boron transporter of two cultivars

BACKGROUND

Essential micronutrient Boron (B) plays crucial roles in plant survival and reproduction but becomes toxic in higher quantities. Although plant cells have different B transport systems, B homeostasis is mainly maintained by two transporter protein families: B exporters (BOR) and nodulin-26-like intrinsic proteins (NIP). Their diversity and differential expression are responsible for varied B tolerance among plant varieties and species. Longan is a highly admired subtropical fruit with a rising market in China and beyond. In the present study, we cultured Shixia (SX) and Yiduo (YD), two differently characterized Longan cultivars, with foliar B spray. We analyzed their leaf physiology, fruit setting, B content, and boron transporter gene expression of various tissue samples. We also traced some of these genes' subcellular localization and overexpression effects.

RESULTS

YD and SX foliage share similar microstructures, except the mesophyll cell wall thickness is double in YD. The B spray differently influenced their cellular constituents and growth regulators. Gene expression analysis showed reduced BOR genes expression and NIP genes differential spatiotemporal expression. Using green fluorescent protein, two high-expressing NIPs, NIP1 and NIP19, were found to translocate in the transformed tobacco leaves' cell membrane. NIPs transformation of SX pollen was confirmed using magnetic beads and quantified using a fluorescence microscope and polymerase chain reaction. An increased seed-setting rate was observed when YD was pollinated using these pollens. Between the DlNIP1 and DlNIP19 transformed SX pollen, the former germinated better with increasing B concentrations and, compared to naturally pollinated plants, had a better seed-setting rate in YD♀ × SX♂.

CONCLUSION

SX and YD Longan have different cell wall structures and react differently to foliar B spray, indicating distinct B tolerance and management. Two B transporter NIP genes were traced to localize in the plasma membrane. However, under high B concentrations, their differential expression resulted in differences in Jasmonic acid content, leading to differences in germination rate. Pollination of YD using these NIPs transformed SX pollen also showed NIP1 overexpression might overcome the unilateral cross incompatibility between YD♀ × SX♂ and can be used to increase Longan production.

The Brassica napus boron deficient inflorescence transcriptome resembles a wounding and infection response

Oilseed rape and other crops of Brassica napus have a high demand for boron (B). Boron deficiencies result in the inhibition of root growth, and eventually premature flower abortion. Understanding the genetic mechanisms underlying flower abortion in B-limiting conditions could provide the basis to enhance B-efficiency and prevent B-deficiency-related yield losses. In this study, we assessed transcriptomic responses to B-deficiency in diverse inflorescence tissues at multiple time points of soil-grown plants that were phenotypically unaffected by B-deficiency until early flowering. Whilst transcript levels of known B transporters were higher in B-deficient samples, these remained remarkably stable as the duration of B-deficiency increased. Meanwhile, GO-term enrichment analysis indicated a growing response resembling that of a pathogen or pest attack, escalating to a huge transcriptome response in shoot heads at mid-flowering. Grouping differentially expressed genes within this tissue into MapMan functional bins indicated enrichment of genes related to wounding, jasmonic acid and WRKY transcription factors. Individual candidate genes for controlling the "flowering-without-seed-setting" phenotype from within MapMan biotic stress bins include those of the metacaspase family, which have been implicated in orchestrating programmed cell death. Overall temporal expression patterns observed here imply a dynamic response to B-deficiency, first increasing expression of B transporters before recruiting various biotic stress-related pathways to coordinate targeted cell death, likely in response to as yet unidentified B-deficiency induced damage-associated molecular patterns (DAMPs). This response indicates new pathways to target and dissect to control B-deficiency-induced flower abortion and to develop more B-efficient crops.

Transcriptome Analysis in Pyrus betulaefolia Roots in Response to Short-Term Boron Deficiency

Boron (B) deficiency stress is frequently observed in pear orchards and causes a considerable loss of productivity and fruit quality. Pyrus betulaefolia is one of the most important rootstocks that has been widely used in pear production. The present study confirmed that the boron form of different tissues showed various changes, and the free boron content was significantly decreased under the short-term B deficiency condition. Moreover, the ABA and JA content also significantly accumulated in the root after short-term B deficiency treatment. A comprehensive transcriptome analysis of 24 h B deficiency treatment P. betulaefolia root was performed in this study. Transcriptome results revealed a total of 1230 up-regulated and 642 down-regulated differentially expressed genes (DEGs), respectively. B deficiency significantly increased the expression of the key aquaporin gene NIP5-1. In addition, B deficiency also increased the expression of ABA (ZEP and NCED) and JA (LOX, AOS and OPR) synthesis genes. Several MYB, WRKY, bHLH and ERF transcription factors were induced by B deficiency stress, which may relate to the regulation of B uptake and plant hormone synthesis. Overall, these findings suggested that P. betulaefolia root had adaptive responses to short-term B deficiency stress by improved boron absorption ability and hormone (JA and ABA) synthesis. The transcriptome analysis provided further information for understanding the mechanism of the pear rootstock responses to B deficiency stress.

Combination of bacterial N-acyl homoserine lactones primes Arabidopsis defenses via jasmonate metabolism

N-acyl homoserine lactones (AHLs) are important players in plant-bacteria interactions. Different AHL-producing bacteria can improve plant growth and resistance against plant pathogens. In nature, plants may host a variety of AHL-producing bacteria and frequently experience numerous AHLs at the same time. Therefore, a coordinated response to combined AHL molecules is necessary. The purpose of this study was to explore the mechanism of AHL-priming using combined AHL molecules including N-(3-oxo-hexanoyl)-L-homoserine lactone, N-3-oxo-octanoyl-L-homoserine lactone, N-3-oxo-dodecanoyl-L-homoserine lactone, and N-3-oxo-tetradecanoyl-L-homoserine lactone and AHL-producing bacteria including Serratia plymuthica HRO-C48, Rhizobium etli CFN42, Burkholderia graminis DSM17151, and Ensifer meliloti (Sinorhizobium meliloti) Rm2011. We used transcriptome analysis, phytohormone measurements, as well as genetic and microbiological approaches to assess how the combination of structurally diverse AHL molecules influence Arabidopsis (Arabidopsis thaliana). Our findings revealed a particular response to a mixture of AHL molecules (AHL mix). Different expression patterns indicated that the reaction of plants exposed to AHL mix differs from that of plants exposed to single AHL molecules. In addition, different content of jasmonic acid (JA) and derivatives revealed that jasmonates play an important role in AHL mix-induced priming. The fast and stable decreased concentration of COOH-JA-Ile after challenge with the flagellin-derived peptide flg22 indicated that AHL mix modifies the metabolism of jasmonates. Study of various JA- and salicylic acid-related Arabidopsis mutants strengthened the notion that JA homeostasis is involved in AHL-priming. Understanding how the combination of AHLs primes plants for enhanced resistance has the potential to broaden our approaches in sustainable agriculture and will help to effectively protect plants against pathogens.

Arabidopsis ERF012 Is a Versatile Regulator of Plant Growth, Development and Abiotic Stress Responses

The AP2/ERF transcription factors are widely involved in the regulation of plant growth, development and stress responses. Arabidopsis ERF012 is differentially responsive to various stresses; however, its potential regulatory role remains elusive. Here, we show that ERF012 is predominantly expressed in the vascular bundles, lateral root primordium and vein branch points. ERF012 overexpression inhibits root growth, whereas it promotes root hair development and leaf senescence. In particular, ERF012 may downregulate its target genes AtC4H and At4CL1, key players in phenylpropanoid metabolism and cell wall formation, to hinder auxin accumulation and thereby impacting root growth and leaf senescence. Consistent with this, exogenous IAA application effectively relieves the effect of ERF012 overexpression on root growth and leaf senescence. Meanwhile, ERF012 presumably activates ethylene biosynthesis to promote root hair development, considering that the ERF012-mediated root hair development can be suppressed by the ethylene biosynthetic inhibitor. In addition, ERF012 overexpression displays positive and negative effects on low- and high-temperature responses, respectively, while conferring plant resistance to drought, salinity and heavy metal stresses. Taken together, this study provides a comprehensive evaluation of the functional versatility of ERF012 in plant growth, development and abiotic stress responses.

Potassium Deficiency in Rice Aggravates Sarocladium oryzae Infection and Ultimately Leads to Alterations in Endophyte Communities and Suppression of Nutrient Uptake

Sheath rot disease is an emerging fungal disease in rice, whose infection causes severe yield loss. Sarocladium oryzae (S. oryzae) is the major causal agent. Previous study has demonstrated that rice deficiency in potassium (K) aggravates S. oryzae infection. However, the effects of S. oryzae infection on the nutrient-uptake process, endophyte communities, and hormone level of host plant under K-deficiency condition remain unclear, the mechanism of K mediated S. oryzae infection needs to be further study. The present study analyzed alterations in the endophytic community and nutrient-uptake process of host plants through an exogenous inoculation of S. oryzae in pot and hydroponics experiments. S. oryzae infection sharply increased the relative abundance of Ascomycota and decreased the Shannon and Simpson index of the endophytic community. Compared with the K-sufficient rice infected with S. oryzae, K-starved rice infected with S. oryzae (-K + I) increased the relative abundance of Ascomycota in leaf sheaths by 52.3%. Likewise, the -K + I treatment significantly decreased the Shannon and Simpson indexes by 27.7 and 25.0%, respectively. Sufficient K supply increased the relative abundance of Pseudomonas spp. in the host plant. S. oryzae infection profoundly inhibited the nutrient uptake of the host plant. The accumulation of oleic acid and linoleic acid in diseased rice decreased the biosynthesis of jasmonic acid (JA), and the content of JA was lowest in the -K + I treatment, which suppressed K⁺ uptake. These results emphasize the importance of K in resistance to S. oryzae infection by modulating endophyte community diversity and enhancing the nutrient-uptake capacity of the host plant.

Nutrient-hormone relations: Driving root plasticity in plants

Optimal plant development requires root uptake of 14 essential mineral elements from the soil. Since the bioavailability of these nutrients underlies large variation in space and time, plants must dynamically adjust their root architecture to optimize nutrient access and acquisition. The information on external nutrient availability and whole-plant demand is translated into cellular signals that often involve phytohormones as intermediates to trigger a systemic or locally restricted developmental response. Timing and extent of such local root responses depend on the overall nutritional status of the plant that is transmitted from shoots to roots in the form of phytohormones or other systemic long-distance signals. The integration of these systemic and local signals then determines cell division or elongation rates in primary and lateral roots, the initiation, emergence, or elongation of lateral roots, as well as the formation of root hairs. Here, we review the cascades of nutrient-related sensing and signaling events that involve hormones and highlight nutrient-hormone relations that coordinate root developmental plasticity in plants.