Summary• Auxin is essential for many aspects of plant growth and development, including the determination of lateral organ shapes.• Here, the characterization of a dominant Arabidopsis thaliana mutant spl-D (SPOROCYTELESS dominant), and the roles of SPL in auxin homeostasis and plant development, are reported.• The spl-D mutant displayed a severe up-curling leaf phenotype caused by increased expression of SPOROCYTELESS/NOZZLE (SPL/NZZ), a putative transcription factor gene that was previously linked to sporocyte formation. The spl-D plants also displayed pleiotropic developmental defects including fewer lateral roots, simpler venation patterns, and reduced shoot apical dominance. The leaf and floral phenotypes of spl-D and SPL over-expression lines were reminiscent of yucca (yuc) triple and quadruple mutants, suggesting that SPL may regulate auxin homeostasis. Consistent with this hypothesis, it was found that over-expression of SPL led to downregulation of the auxin reporter DR5-GUS, and that many auxin-responsive genes were down-regulated in spl-D leaves. Interestingly, the expression of YUC2 and YUC6, two key genes in auxin biosynthesis, was significantly repressed in spl-D plants.• Taken together with the genetic and phenotypic analysis of spl-D/yuc6-D double mutant, these data suggest that SPL may regulate auxin homeostasis by repressing the transcription of YUC2 and YUC6 and participate in lateral organ morphogenesis.

Background Acquired resistance of 5-fluorouracil (5-FU) remains a clinical challenge in colorectal cancer (CRC), and efforts to develop targeted agents to reduce resistance have not yielded success. Metabolic reprogramming is a key cancer hallmark and confers several tumor phenotypes including chemoresistance. Glucose metabolic reprogramming events of 5-FU resistance in CRC has not been evaluated, and whether abnormal glucose metabolism could impart 5-FU resistance in CRC is also poorly defined. Methods Three separate acquired 5-FU resistance CRC cell line models were generated, and glucose metabolism was assessed by measuring glucose and lactate utilization, RNA and protein expressions of glucose metabolism-related enzymes and changes of intermediate metabolites of glucose metabolite pool. The protein levels of hypoxia inducible factor 1α (HIF-1α) in primary tumors and circulating tumor cells of CRC patients were detected by immunohistochemistry and immunofluorescence. Stable HIF1A knockdown in cell models was established with a lentiviral system. The influence of both HIF1A gene knockdown and pharmacological inhibition on 5-FU resistance in CRC was evaluated in cell models in vivo and in vitro. Results The abnormality of glucose metabolism in 5-FU-resistant CRC were described in detail. The enhanced glycolysis and pentose phosphate pathway in CRC were associated with increased HIF-1α expression. HIF-1α-induced glucose metabolic reprogramming imparted 5-FU resistance in CRC. HIF-1α showed enhanced expression in 5-FU-resistant CRC cell lines and clinical specimens, and increased HIF-1α levels were associated with failure of fluorouracil analog-based chemotherapy in CRC patients and poor survival. Upregulation of HIF-1α in 5-FU-resistant CRC occurred through non-oxygen-dependent mechanisms of reactive oxygen species-mediated activation of PI3K/Akt signaling and aberrant activation of β-catenin in the nucleus. Both HIF-1α gene knock-down and pharmacological inhibition restored the sensitivity of CRC to 5-FU. Conclusions HIF-1α is a potential biomarker for 5-FU-resistant CRC, and targeting HIF-1a in combination with 5-FU may represent an effective therapeutic strategy in 5-FU-resistant CRC.

SUMMARYMap-based cloning has been widely used to identify genes responsible for mutant phenotypes in Arabidopsis, especially those mutants generated by EMS or fast neutron mutagenesis. The success of map-based cloning relies on the availability of molecular markers that distinguish the polymorphisms between two Arabidopsis ecotypes. So far, most molecular markers in Arabidopsis have been generated by individual laboratories or the Arabidopsis Information Resource (TAIR). However, the TAIR markers, which are distributed unevenly on the five Arabidopsis chromosomes, only cover approximately 25% of the Arabidopsis BACs. Designing and testing molecular markers is still a time-consuming endeavor. Here we report the construction of a high-resolution BAC-based Arabidopsis mapping platform (AMP), using Col-0 and Ler as model ecotypes. The AMP comprises 1346 markers (1073 INDEL and 273 CAPS/dCAPS markers), of which 971 were newly designed and experimentally confirmed, 179 were from published papers and 196 were TAIR markers. These AMP markers cover 1186 BACs, 1121 of which are in non-centromere regions, representing approximately 75% of the Arabidopsis BACs in non-centromere regions. All the marker information is included on the AMP website (http://amp.genomics.org.cn/) for easy access and download, and sets of standard markers for initial chromosomal localization of a particular gene are recommended. The feasibility of using the AMP to map mutated genes is also discussed.

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Pre-harvest sprouting (PHS), the germination of grain before harvest, is a serious problem resulting in wheat yield and quality losses.Here, we mapped the PHS resistance gene PHS-3D from synthetic hexaploid wheat to a 2.4 Mb presence-absence variation (PAV) region and found that its resistance effect was attributed to the pleiotropic Myb10-D by integrated omics and functional analyses.Three haplotypes were detected in this PAV region among 262 worldwide wheat lines and 16 Aegilops tauschii, and the germination percentages of wheat lines containing Myb10-D was approximately 40% lower than that of the other lines. Transcriptome and metabolome profiling indicated that Myb10-D affected the transcription of genes in both the flavonoid and abscisic acid (ABA) biosynthesis pathways, which resulted in increases in flavonoids and ABA in transgenic wheat lines. Myb10-D activates 9-cis-epoxycarotenoid dioxygenase (NCED) by biding the secondary wall MYB-responsive element (SMRE) to promote ABA biosynthesis in early wheat seed development stages.We revealed that the newly discovered function of Myb10-D confers PHS resistance by enhancing ABA biosynthesis to delay germination in wheat. The PAV harboring Myb10-D associated with grain color and PHS will be useful for understanding and selecting white grained PHS resistant wheat cultivars.

Plant hormones are small organic molecules that influence almost every aspect of plant growth and development. Genetic and molecular studies have revealed a large number of genes that are involved in responses to numerous plant hormones, including auxin, gibberellin, cytokinin, abscisic acid, ethylene, jasmonic acid, salicylic acid, and brassinosteroid. Here, we develop an Arabidopsis hormone database, which aims to provide a systematic and comprehensive view of genes participating in plant hormonal regulation, as well as morphological phenotypes controlled by plant hormones. Based on data from mutant studies, transgenic analysis and gene ontology (GO) annotation, we have identified a total of 1026 genes in the Arabidopsis genome that participate in plant hormone functions. Meanwhile, a phenotype ontology is developed to precisely describe myriad hormone-regulated morphological processes with standardized vocabularies. A web interface (http://ahd.cbi.pku.edu.cn) would allow users to quickly get access to information about these hormone-related genes, including sequences, functional category, mutant information, phenotypic description, microarray data and linked publications. Several applications of this database in studying plant hormonal regulation and hormone cross-talk will be presented and discussed.

We previously reported that Arabidopsis indole-3-acetic acid (IAA)-methyltransferase-1 (IAMT1) catalyzes the conversion of IAA, an essential phytohormone, to methyl-IAA (MeIAA) and that IAMT1 plays an important role in leaf development. Here, we present the possible mechanisms of action of MeIAA in Arabidopsis. We showed that MeIAA was more potent than IAA in the inhibition of hypocotyl elongation and that MeIAA and naphthalene-acetic acid (NAA), but not IAA, rescued the hypocotyl gravitropic defects in dark-grown aux1. However, MeIAA was less potent than IAA in the inhibition of primary root elongation in light-grown seedlings, and could not rescue the agravitropic root phenotype of aux1. MeIAA had a stronger capacity to induce lateral roots than both IAA and NAA and rescued the defective lateral root phenotype of aux1 seedlings. However, its capacity to induce root hairs was weaker than IAA and NAA and did not rescue the defective root hair phenotype of aux1 seedlings. These data indicate that MeIAA is an inactive form of IAA. The different sensitivities to MeIAA among different organs probably resulted from different expression localization and capacities of a putative MeIAA esterase to convert MeIAA to IAA.

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