Two aquaporins, SIP1;1 and PIP1;2, mediate water transport for pollen hydration in the pistil.

Pollination is the crucial initial step that brings together the male and female gametophytes, and occurs at the surface of the stigmatic papilla cell in . After pollen recognition, pollen hydration is initiated as a second critical step to activate desiccated mature pollen grains for germination, and thus water transport from pistil to pollen is essential for this process. In this study, we report a novel aquaporin-mediated water transport process in the papilla cell as a control mechanism for pollen hydration.

Double-Locking Mechanism of Self-Compatibility in : The Synergistic Effect of Transcriptional Depression and Disruption of Coding Region in the Male Specificity Gene.

Self-compatibility in represents the relatively recent disruption of ancestral obligate cross pollination, recognized as one of the prevalent evolutionary pathways in flowering plants, as noted by Darwin. Our previous study found that inversion of the male specificity gene (/) disrupted self-incompatibility, which was restored by overexpressing the with the reversed inversion. However, in has other mutations aside from the pivotal inversion, in both promoter and coding regions, with probable effects on transcriptional regulation.

Abscisic acid-mediated developmental flexibility of stigmatic papillae in response to ambient humidity in Arabidopsis thaliana.

Stigmatic papillae develop at the apex of the gynoecium and play an important role as a site of pollination. The papillae in Brassicaceae are of the dry and unicellular type, and more than 15,000 genes are expressed in the papillae; however, the molecular and physiological mechanisms of their development remain unknown. We found that the papillae in Arabidopsis thaliana change their length in response to altered ambient humidity: papillae of flowers incubated under high humidity elongated more than those under normal humidity conditions.

The Arabidopsis transcription factor NAI1 is required for enhancing the active histone mark but not for removing the repressive mark on PYK10, a seedling-specific gene upon embryonic-to-postgerminative developmental phase transition.

We have recently shown that the expression onset of a seedling-specific gene, PYK10, occurs in a cell-by-cell manner upon the transition from the embryonic to the postgerminative phase and during embryogenesis in seed maturation regulator mutants such as lec1, and implicated epigenetic mechanisms in the process. Here, the role of the NAI1 transcription factor required for PYK10 expression in the developmental switching of PYK10 was investigated. The cell-by-cell onset of PYK10-EGFP in lec1 embryo was still observed in the nai1 background, but at greatly reduced levels.

Rice SNF2 family helicase ENL1 is essential for syncytial endosperm development.

The endosperm of cereal grains represents the most important source of human nutrition. In addition, the endosperm provides many investigatory opportunities for biologists because of the unique processes that occur during its ontogeny, including syncytial development at early stages. Rice endospermless 1 (enl1) develops seeds lacking an endosperm but carrying a functional embryo.

Cell-by-cell developmental transition from embryo to post-germination phase revealed by heterochronic gene expression and ER-body formation in Arabidopsis leafy cotyledon mutants.

LEC1, LEC2, FUS3 and ABI3 (collectively abbreviated LEC/ABI3 here) are required for embryo maturation and have apparent roles in repressing post-germinative development. lec mutant embryos exhibit some heterochronic characteristics, as exemplified by the development of true leaf-like cotyledons during embryogenesis. Although the roles of LEC/ABI3 as positive regulators of embryo maturation have been extensively studied, their roles in the negative regulation of post-germinative development have not been explored in detail.

Ectopic gene expression and organogenesis in Arabidopsis mutants missing BRU1 required for genome maintenance.

Chromatin reconstitution after DNA replication and repair is essential for the inheritance of epigenetic information, but mechanisms underlying such a process are still poorly understood. Previously, we proposed that Arabidopsis BRU1 functions to ensure the chromatin reconstitution. Loss-of-function mutants of BRU1 are hypersensitive to genotoxic stresses and cause release of transcriptional gene silencing of heterochromatic genes.

Diverse roles and mechanisms of gene regulation by the Arabidopsis seed maturation master regulator FUS3 revealed by microarray analysis.

The FUSCA3 (FUS3) transcription factor is considered a master regulator of seed maturation because a wide range of seed maturation events are impaired in its defective mutant. To identify comprehensively genes under the control of FUS3, two types of microarray experiments were performed. First, transgenic plants in which FUS3 expression could be induced by the application of estrogen (ESTR) were used to identify any genes up-regulated in young seedlings of Arabidopsis in response to the ectopic expression of FUS3.

Arabidopsis transcription factors, RAV1 and RAV2, are regulated by touch-related stimuli in a dose-dependent and biphasic manner.

Transcription factors, RAV1 and RAV2 from Arabidopsis thaliana, contain two distinct DNA-binding domains, AP2/EREBP and B3, both of which are uniquely found in plants. We found that transcripts of RAV1 and RAV2 were upregulated transiently by touch-related mechanical stimuli. However, the temporal expression patterns of RAV1 and RAV2 differed from those of known touch-induced genes.

Arabidopsis NF-YB subunits LEC1 and LEC1-LIKE activate transcription by interacting with seed-specific ABRE-binding factors.

LEAFY COTYLEDON 1 (LEC1) plays vital roles in the regulation of seed maturation in Arabidopsis. LEC1 encodes a homolog of yeast HAP3 or mammalian NF-YB/CBF-A subunit of trimeric CCAAT binding factor (CBF). Among the nine paralogs of NF-YB in Arabidopsis, LEC1-LIKE (L1L) is most closely related to LEC1, and can complement the lec1 mutation when expressed under the control of the LEC1 promoter.

Abscisic acid-activated SNRK2 protein kinases function in the gene-regulation pathway of ABA signal transduction by phosphorylating ABA response element-binding factors.

The plant hormone abscisic acid (ABA) induces gene expression via the ABA-response element (ABRE) present in the promoters of ABA-regulated genes. A group of bZIP proteins have been identified as ABRE-binding factors (ABFs) that activate transcription through this cis element. A rice ABF, TRAB1, has been shown to be activated via ABA-dependent phosphorylation.

Indirect ABA-dependent regulation of seed storage protein genes by FUSCA3 transcription factor in Arabidopsis.

The key transcription factors that control seed maturation, ABSCISIC ACID INSENSITIVE3 (ABI3) and FUSCA3 (FUS3), share homologous DNA-binding domains. Regulation of seed storage protein genes At2S3 and CRC by ABI3 and FUS3 was investigated using transgenic plants in which ABI3 and FUS3 could be ectopically induced by steroid hormones. Like ABI3, the presence of FUS3 led to expression of At2S3 and CRC in vegetative tissues.

LEAFY COTYLEDON1 controls seed storage protein genes through its regulation of FUSCA3 and ABSCISIC ACID INSENSITIVE3.

Arabidopsis ABSCISIC ACID INSENSEITIVE3 (ABI3), FUSCA3 (FUS3) and LEAFY COTYLEDON1 (LEC1) encode key transcription factors that control seed maturation events, including seed storage protein (SSP) accumulation. Although lec1 mutations are known to down-regulate SSP gene expression as the fus3 or abi3 mutation does, the mechanisms by which LEC1 regulates SSP gene expression are largely unknown compared with the mechanisms utilized by FUS3 or ABI3. We expressed LEC1 ectopically in transgenic plants using an artificial dexamethasone (Dex) induction system.

Differential activation of the rice sucrose nonfermenting1-related protein kinase2 family by hyperosmotic stress and abscisic acid.

To date, a large number of sequences of protein kinases that belong to the sucrose nonfermenting1-related protein kinase2 (SnRK2) family are found in databases. However, only limited numbers of the family members have been characterized and implicated in abscisic acid (ABA) and hyperosmotic stress signaling. We identified 10 SnRK2 protein kinases encoded by the rice (Oryza sativa) genome.

Abscisic acid-induced transcription is mediated by phosphorylation of an abscisic acid response element binding factor, TRAB1.

The rice basic domain/Leu zipper factor TRAB1 binds to abscisic acid (ABA) response elements and mediates ABA signals to activate transcription. We show that TRAB1 is phosphorylated rapidly in an in vivo labeling experiment and by phosphatase-sensitive mobility shifts on SDS-polyacrylamide gels. We had shown previously that a chimeric promoter containing GAL4 binding sites became ABA inducible when a GAL4 binding domain-TRAB1 fusion protein was present.

Temporal and spatial expression pattern of the OSVP1 and OSEM genes during seed development in rice.

The spatial and temporal expression patterns of the rice VP1 (OSVP1) gene, as well as the OSEM gene which it controls, were studied during seed development by in situ hybridization and immuno-localization techniques. The expression of OSVP1 could be detected in embryos as early as 2-3 d after pollination (DAP) and thereafter became preferentially localized to shoot, radicle and vascular tissues during the embryo development at both the mRNA and protein levels. In the aleurone layers, OSVP1 mRNA and protein were detected after 6 DAP.

Experimentally determined sequence requirement of ACGT-containing abscisic acid response element.

The sequence requirement of the ACGT-containing abscisic acid response element (ABRE) was analyzed by systematically substituting the bases surrounding the ACGT-core of motif A, the principal ABRE of the rice gene, OSEM: This was done within the context of a 55-bp promoter fragment that minimally confers ABA-responsiveness to a heterologous promoter. Based on this analysis, the sequence requirement of the ACGT-containing ABRE was determined as ACGTG G/T C, which matched very well with the consensus derived from sequence comparison of ABA-responsive promoters.