Mechanism of the Increase of Polyphenol Oxidase Activity in Pineapple Fruit Induced by GA3

No increase in polyphenol oxidase (PPO) activity was found by addition of GA3 solution in the enzyme extraction. But acid phosphatase activity was found to be increased in pineapple fruit (Armnas comosus (L.) Merr. ) treated with GA3, which was mainly caused by the significant increase in inorganic phosphate (Pi) content. Phospholipase D activities decreased gradually during the period of fruit ripening but GA3 treatment slowed down these processes. On the other hand, the increase of PPO activities in fruit treated with GA3 was enhanced by the addition of ABA treatment.     

Genome-wide identification of the BURP domain-containing genes in Phaseolus vulgaris

Plant-specific BURP domain-containing proteins have an essential role in the plant''s development and stress responses. Although BURP domain-containing proteins have been identified in several plant species, genome-wide analysis of the BURP gene family has not been investigated in the common bean. In the present study, we identified 11 BURP family members in the common bean (Phaseolus vulgaris) genome with a comprehensive in silico analysis. Pairwise alignment and phylogenetic analyses grouped PvBURP members into four subfamilies [RD-22 like (3), PG1β-like (4), BNM2-like (3), and USP-like (1)] according to their amino acid motifs, protein domains and intron–exon structure. The physical and biochemical characteristics of amino acids, motif and intron–exon structure, and cis-regulatory elements of BURPs members were determined. Promoter regions of BURP members included stress, light, and hormone response-related cis-elements. Therefore, expression profiles of PvBURP genes were identified with in silico tools and qRT-PCR analyses under stress (salt and drought) and hormone treatment (ABA, IAA) in the current study. While significant activity changes were not observed in BURP genes in RNA-seq data sets related to salt stress, it was determined that some BURP genes were expressed differently in those with drought stress. We identified 12 different miRNA, including miRNA395, miRNA156, miRNA169, miRNA171, miRNA319, and miRNA390, targeting the nine PvBURP genes using two different in silico tools based on perfect or near‐perfect complementarity to their targets. Here we present the first study to identify and characterize the BURP genes in common bean using whole-genome analysis, and the findings may serve as a reference for future functional research in common bean.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-01052-9.     

Effects of Periodical Soil Drying and Leaf Water Potential on the Sensitivity of Stomatal Response to Xylem ABA

The study on the changes of stomatal sensitivity in relation to xylem ABA during periodical soil drying and the effect of leaf water status on the stomatal sensitivity has confirmed that xylem ABA concentration is a good indicator of soil water status around roots and the relation between xylem ABA concentration and predawn leaf water potential remained constant during the three consecutive soil drying cycles based on the slopes of the fitted lines. The sensitivity of stomata to xylem ABA increased substantially as the soil drying cycles progressed, and the xylem ABA concentration needed to cause a 50% decrease of stomatal conductance was as low as 550 mnoL/L in the next two soil drying cycle, as compared with the 750 nmol/L ABA in the first cycle of soil drying. The results using the split-root system showed that leaf water deficit significantly enhanced the stomatal response to xylem ABA and the xylem ABA concentration needed to cause a 50% decrease in stomatal conductance was 2 to 4 times smaller in the whole-root-drying treatment than those in the semi-root- drying treatment. These results suggested that the sensitivity of stomata to xylem ABA concentration is not a fixed characteristic.     

水分胁迫下山黧豆中ABA及ODAP的积累研究

用PEG、PEG+ABA、ABA分别处理15d龄的山黧豆幼苗,取其叶片为实验材料,测定内源ABA、ODAP、MDA和H₂O₂含量以及几种抗氧化酶活性,结果表明,与对照相比处理材料叶片中ABA和ODAP含量显著增加;外源ABA的加入降低了PEG胁迫引起的MDA和H₂O₂含量的增加,延缓了PEG胁迫引起的CAT活性的衰减,提高了GR活性.用外源ABA长时间处理山黧豆,发现叶片中ABA含量显著增加,随后出现ODAP的积累;ABA处理初期(0～3d)对叶片中活性氧代谢影响不大,随着ABA处理时间的延长(7～15d),可引起叶片中SOD、POD、CAT、GR活性的降低,MDA、H₂O₂含量的增加,表明ABA确实可促进ODAP的积累.     

Pretreatments,conditioned medium and co-culture increase the incidence of somatic embryogenesis of different Cichorium species

Somatic embryogenesis (SE) in Cichorium involves dedifferentiation and redifferentiation of single cells and can be induced by specific in vitro culture conditions. We have tested the effect of various treatments on the incidence of SE (ISE) of an interspecific embryogenic hybrid (C. endivia x C. intybus) and of different commercial chicories (C. endivia and C. intybus) that are typically recalcitrant to SE in standard culture conditions. We found that the ISE of the hybrid is significantly increased by pretreatment of tissues by submersion in solutions of glycerol, abscisic acid, spermine, putrescine or of combinations of these compounds. Interestingly, the most efficient of these pretreatments also had an unexpectedly high effect on the ISE of the C. intybus cultivars. The ISE of the hybrid and of the commercial chicories were increased when explants were co-cultured with highly embryogenic chicory explants or when they were cultured in conditioned medium. These observations established that unidentified SE-promoting factors are released in the culture medium. HPLC analyses of secreted Arabino-Galactan Proteins (AGPs), which are known to stimulate SE, did not allow identifying a fraction containing differentially abundant AGP candidates. However, pointing to their role in promoting SE, we found that the hybrid had a drastically higher ISE when amino sugars and L-Proline, the putative precursors of secreted AGPs, were both added to the medium.     

The influence of salt stress on ABA and auxin concentrations in two maize cultivars differing in salt resistance

The plant hormones abscisic acid (ABA) and auxin (IAA, IBA) play important roles in plant responses to environmental stresses such as salinity. Recent breeding improvements in terms of salt resistance of maize have lead to a genotype with improved growth under saline conditions. By comparing this salt-resistant hybrid with a sensitive hybrid, it was possible to show differences in hormone concentrations in expanding leaves and roots. In response to salinity, the salt-resistant maize significantly increased IBA concentrations in growing leaves and maintained IAA concentration in roots. These hormonal adaptations may help to establish favorable conditions for growth-promoting agents such as β-expansins and maintain growth of resistant maize hybrids under salt stress. Moreover, ABA concentrations significantly increased in resistant maize leaves under salt stress, which may contribute to acidifying the apoplast, which in turn is a prerequisite for growth.     

Characterization of an Abc1 kinase family gene OsABC1-2 conferring enhanced tolerance to dark-induced stress in rice

Leaf senescence is a complex and highly organized process resulting in numerous changes of gene expression and metabolic procedures. However, the exact mechanisms underlying these changes are not well understood. In this study, we reported a rice (Oryza sativa) T-DNA insertion mutant impaired in an Abc1 kinase family gene with a dwarf and pale-green phenotype. The mutant showed reduced pigment content and photosynthetic efficiency and increased superoxide dismutase activity in leaves. The mutated gene, designated OsABC1-2, is expressed primarily in green tissues and/or organs and encodes a protein localized in chloroplast envelope. Expression of the gene was drastically suppressed by dark treatment. Overexpression of the gene in rice enhanced tolerance to prolonged dark-induced stress. Phylogenetic analysis revealed that the plant Abc1 proteins could be divided into three subgroups and OsAbc1-2 resides in a subgroup with potential chloroplast origin. Our results suggest that divergence has occurred among plant Abc1 family and chloroplast Abc1 kinases play potential roles in regulating dark-induced senescence of plants.     

Isolation and expression analysis of proline metabolism-related genes in Chrysanthemum lavandulifolium

Proline plays a significant role in plant resistance to abiotic stresses, and its level is determined by a combination of synthesis, catabolism and transport. The primary proteins involved are Δ¹-pyrroline-5-carboxylate synthetase (P5CS), proline dehydrogenase (PDH) and proline transporter (ProT). To utilise proline metabolism to improve the stress resistance of Chrysanthemum × morifolium, we isolated two P5CS-homologous genes (ClP5CS1 and ClP5CS2), one PDH gene (ClPDH) and four ProT-homologous genes (ClProT1-4) (GenBANK accession numbers: KF743136–KF743142) from Chrysanthemum lavandulifolium, which is closely related to chrysanthemums and exhibits strong resistance to stresses. Expression analysis of these genes in different organs and under various stresses indicated that ClP5CSs showed substantial constitutive expression, while ClPDH was only strongly expressed in the capitulum and was inhibited under most stresses. The expression patterns of four ClProT genes presented characteristics of organ specificity and disparity under stresses. Above all, the expression of ClProT2 was restricted to above-ground organs, especially strong in the capitulum and could be obviously induced by various stress conditions. Promoters of ClPDH and ClProTs contained many cis-acting regulatory elements involved in stress responses and plant growth and development. High levels of free proline were found in flower buds, the capitulum under the non-stress condition and later periods of stress conditions except cold treatment. Interestingly, organ specificity and disparity also exist in the level of free proline under different stress conditions. Our study indicates that ClProTs play significant roles in proline accumulation and stress responses, and that ClProT2 could be used to genetically modify the stress resistance of chrysanthemums. In addition, proline metabolism might be closely related to plant flowering and floral development.     

Characteristics of a Diurnal Rhythm of Assimilate Translocation in Grapevine Plants

Characteristics of photoassimilate efflux from the leaves of grapevine (Vitis vinifera L., var. Rkatsiteli) plants under natural conditions and upon darkening, defoliation, and ABA treatment at short exposures (2, 6, and 24 h) as well as diurnal pattern of starch content in the leaves were investigated. Translocation of assimilates from the leaves of grapevine usually occurred at night and started after 20:00 or 21:00. However, such pattern of translocation was not strictly determinated and could be changed upon the action of some factors. Darkening, defoliation, and treatment with ABA initiated the translocation of photoassimilates from the leaves in the daytime. Darkening and ABA treatment turned out to be more efficient than defoliation. Darkening and defoliation significantly changed the character of partitioning of photoassimilates in the stem. We corroborated the opinion that in grapevine, the efflux of assimilates from source leaves is also governed by the feedback mechanism and probably much depends on the level of carbohydrates.