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Plant root systems play a pivotal role in plant physiology and exhibit diverse phenotypic traits. Understanding the genetic mechanisms governing root growth and development in model plants like maize is crucial for enhancing crop resilience to drought and nutrient limitations. This study focused on identifying and characterizing ZmPILS6, an annotated auxin efflux carrier, as a key regulator of various crown root traits in maize. ZmPILS6-modified roots displayed reduced network area and suppressed lateral root formation, which are desirable traits for the "steep, cheap, and deep" ideotype. The research revealed that ZmPILS6 localizes to the endoplasmic reticulum and plays a vital role in controlling the spatial distribution of indole-3-acetic acid (IAA or "auxin") in primary roots. The study also demonstrated that ZmPILS6 can actively efflux IAA when expressed in yeast. Furthermore, the loss of ZmPILS6 resulted in significant proteome remodeling in maize roots, particularly affecting hormone signaling pathways. To identify potential interacting partners of ZmPILS6, a weighted gene coexpression analysis was performed. Altogether, this research contributes to the growing knowledge of essential genetic determinants governing maize root morphogenesis, which is crucial for guiding agricultural improvement strategies., Competing Interests: Competing interests statement:The authors declare no competing interest.

The lipid-derived hormones jasmonates (JAs) play key functions in a wide range of physiological and developmental processes that regulate growth, secondary metabolism and defense against biotic and abiotic stresses. In this connection, biosynthesis, tissue-specific distribution, metabolism, perception, signaling of JAs have been the target of extensive studies. In recent years, the involvement of JAs signaling pathway in the regulation of growth and adaptive responses to environmental challenges has been further examined. However, JAs-mediated mechanisms underlying the transition from 'growth mode' to 'adaptive mode' remain ambiguous. Combined analysis of transgenic lines deficient in JAs signaling in conjunction with the data from JAs-treated plants revealed the function of these hormones in rewiring of central metabolism. The collective data illustrate JAs-mediated decrease in the levels of metabolites associated with active growth such as sucrose, raffinose, orotate, citrate, malate, and an increase in phosphorylated hexoses, responsible for the suppression of growth and photosynthesis, concurrent with the induction of protective metabolites, such as aromatic and branched-chain amino acids, and aspartate family of metabolites. This finding provides an insight into the function of JAs in shifting the central metabolism from the production of growth-promoting metabolites to protective compounds and expands our understanding of the role of JAs in resource allocation in response to environmental challenges., (� The Author(s) 2019. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

HYDROPEROXIDE LYASE (HPL) genes encode enzymes that catalyze the cleavage of fatty acid hydroperoxides into aldehydes and oxoacids. There are three HPLs in rice (Oryza sativa), designated OsHPL1 through OsHPL3. To explore the possibility of differential functional activities among these genes, we have examined their expression patterns and biochemical properties of their encoded products. Transcript analysis indicates that these genes have distinct patterns and levels of expression. OsHPL1 is ubiquitously expressed, OsHPL2 is expressed in the leaves and leaf sheaths, whereas OsHPL3 is wound inducible and expressed exclusively in leaves. OsHPLs also differ in their substrate preference as determined by in vitro enzyme assays using 9-/13-hydroperoxy linolenic and 9-/13-hydroperoxy linoleic acids as substrates. OsHPL1 and OsHPL2 metabolize 9-/13-hydroperoxides, whereas OsHPL3 metabolizes 13-hydroperoxy linolenic acid exclusively. Sequence alignments of the HPL enzymes have identified signature residues potentially responsible for the substrate specificity/preference of these enzymes. All three OsHPLs are chloroplast localized as determined by chloroplast import assays and green fluorescent protein (GFP) fusion studies. Aldehyde measurements in transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing individual OsHPL-GFP fusions indicate that all rice HPLs are functional in a heterologous system, and each of them generates a distinct signature of the metabolites. Interestingly, these aldehydes were only detectable in leaves, but not in roots, despite similar levels of OsHPL-GFP proteins in both tissues. Similarly, there were undetectable levels of aldehydes in rice roots, in spite of the presence of OsHPL1 transcripts. Together, these data suggest that additional tissue-specific mechanism(s) beyond transcript and HPL enzyme abundance, regulate the levels of HPL-derived metabolites.

The Mexican shrub Cuphea hookeriana accumulates up to 75% caprylate (8:0) and caprate (10:0) in its seed oil. An acyl-ACP thioesterase cDNA from C. hookeriana, designated Ch FatB2, has been identified, which, when expressed in Escherichia coli, provides thioesterase activity specific for 8:0- and 10:0-ACP substrates. Expression of this clone in seeds of transgenic canola, an oilseed crop that normally does not accumulate any 8:0 and 10:0, resulted in a dramatic increase in the levels of these two fatty acids accompanied by a preferential decrease in the levels of linoleate (18:2) and linolenate (18:3). The Ch FatB2 differs from Ch FatB1, another Cuphea hookeriana thioesterase reported recently, in both substrate specificity and expression pattern. The Ch FatB1 has a broad substrate specificity with strong preference for 16:0-ACP and is expressed throughout the plant; whereas Ch FatB2 is specific for 8:0/10:0-ACP and its expression is confined to the seed. It is proposed that the amplified expression of Ch FatB2 in the embryo provides the hydrolytic enzyme specificity determining the fatty acyl composition of Cuphea hookeriana seed oil.

The seed oil of Cuphea palustris has an unusual fatty-acyl composition, whereby the principal fatty-acyl groups, myristate (64%) and caprylate (20%), differ by more than two methylenes. We have isolated two thioesterase (TE) cDNAs from C. palustris, encoding proteins designated Cp FatB1 and Cp FatB2, which, when expressed in Escherichia coli, have TE activities specific for 8:0/10:0- and 14:0/16:0-acyl carrier protein substrates, respectively. The specific activities of the recombinant affinity-purified enzymes indicate that Cp FatB2 is kinetically superior to Cp FatB1. This result is consistent with the predominance of 14:0 in the seed oil, despite apparently equal mRNA abundance of the two transcripts in the seed. In C. palustris the expression of both sequences is confined to the seed tissues. Based on these findings we propose that these two enzymes are major factors determining the bimodal chain-length composition of C. palustris oil. Analysis of the immature and mature seed oil by reverse-phase high-performance liquid chromatography confirmed that the principal triglycerides contain both 8:0 and 14:0. This result indicates that both fatty acids are synthesized at the same time and in the same cells at all developmental stages during oil deposition, suggesting that the two TEs act together in the same fatty acid synthesis system.

Complementary DNA clones encoding a DNA-binding factor have been obtained from Arabidopsis by DNA hybridization with a GT-2 factor cDNA clone from rice. The GT-2 gene appears to be present as a single copy in the Arabidopsis genome and is transcribed as a 2.1 kb mRNA which is not light-regulated. The longest open reading frame in the sequenced clones predicts a protein of 65 kDa, beginning with the first in-frame methionine. The protein contains basic, acidic, and proline/glutamine-rich motifs and has significant amino acid sequence homology to the rice GT-2 factor, including three regions of 50-75 amino acids each of greater than 60% identity. Two of these regions are predicted to form similar trihelix structures postulated to be involved in selective binding to specific variations of a GT-box motif DNA sequence found in the promoter regions of several plant genes. Except for weak similarity to a tobacco GT-box binding factor, GT-1a/B2F, Arabidopsis GT-2 has no similarity to other sequences in the databases. DNA-binding studies show that Arabidopsis GT-2 has binding characteristics similar to those of the rice GT-2 factor, but dissimilar to those of the tobacco GT-1a/B2F factor. The data indicate that a DNA-binding factor containing domains of similar structure and target-sequence specificity has been conserved between monocots and dicots.

The light-dependent accumulation of the P700 chlorophyll a protein of the photosystem I reaction center has been studied in greening barley (Hordeum vulgare L.) seedlings. Immunoblot analysis of total cellular protein fractions and immunogold labelling of the P700 chlorophyll a protein in ultrathin sections of Lowicryl-embedded leaf tissue revealed that the concentration of this chlorophyll-binding protein in plastids of dark-grown barley seedlings is below the limit of detection. Upon illumination with white light, a rapid accumulation of this protein is induced. This light effect seems not to be regulated at the level of transcription. The gene for the P700 chlorophyll a protein has been mapped within the large single-copy region of the plastid DNA of barley. High levels of transcripts of this gene are present already in dark-grown seedlings and remain fairly constant throughout an extended illumination period. Polysomes were isolated from etioplasts and chloroplasts. The same high relative concentration of mRNA encoding the P700 chlorophyll a protein was present in both polysome fractions. This result suggests that the light-dependent accumulation of the P700 chlorophyll a protein during chloroplast formation in barley seedlings is regulated at the translational, or posttranslational, level.