SummaryRecent studies have shown that molecular control of inner floral organ identity appears to be largely conserved between monocots and dicots, but little is known regarding the molecular mechanism underlying development of the monocot outer floral organ, a unique floral structure in grasses. In this study, we report the cloning of the rice EXTRA GLUME1 (EG1) gene, a putative lipase gene that specifies empty-glume fate and floral meristem determinacy. In addition to affecting the identity and number of empty glumes, mutations in EG1 caused ectopic floral organs to be formed at each organ whorl or in extra ectopic whorls. Iterative glumelike structures or new floral organ primordia were formed in the presumptive region of the carpel, resulting in an indeterminate floral meristem. EG1 is expressed strongly in inflorescence primordia and weakly in developing floral primordia. We also found that the floral meristem and organ identity gene OsLHS1 showed altered expression with respect to both pattern and levels in the eg1 mutant, and is probably responsible for the pleiotropic floral defects in eg1. As a putative class III lipase that functionally differs from any known plant lipase, EG1 reveals a novel pathway that regulates rice empty-glume fate and spikelet development.

SummaryThe evolutionarily conserved MAP65 family proteins bundle anti-parallel microtubules (MTs). In Arabidopsis thaliana, mutations in the MAP65-3 gene lead to serious defects in MT organization in the phragmoplast and cause failures in cytokinesis. However, the functions of other Arabidopsis MAP65 isoforms are largely unknown.MAP65 functions were analyzed based on genetic interactions among different map65 mutations. Live-cell imaging and immunolocalization experiments revealed dynamic activities of two closely related MAP65 proteins in dividing cells.The map65-4 mutation caused synthetic lethality with map65-3 although map65-4 alone did not cause a noticeable phenotype. Furthermore, the introduction of an extra copy of the MAP65-4 gene significantly suppressed defects in cytokinesis and seedling growth caused by map65-3 because of restoring MT engagement in the spindle midzone. During mitosis, MAP65-4 first appeared at the preprophase band and persisted at the cortical division site afterwards. It was also concentrated on MTs in the spindle midzone and the phragmoplast. In the absence of MAP65-3, MAP65-4 exhibited greatly enhanced localization in the midzone of developing phragmoplast.Therefore, we have uncovered redundant but differential contributions of MAP65-3 and MAP65-4 to engaging and bundling anti-parallel MTs in the phragmoplast and disclosed a novel action of MAP65-4 at the cortical cell division site.

Fungal immunomodulatory proteins (FIPs) have been identified from a series of fungi, especially in Ganoderma species. However, little is known about the FIPs from G. applanatum. In this study, two novel FIP genes, termed as FIP-gap1 and FIP-gap2, were cloned from G. applanatum, characterized and functionally expressed after codon optimization in Pichia pastoris GS115. Results showed that FIP-gap1 and FIP-gap2 comprised 342-bp encoding peptides of 113 amino acids, which shared a high homology with other Ganoderma FIPs. The yield of recombinant FIP-gap1 and FIP-gap2 increased significantly after codon optimization and reached 247.4 and 197.5 mg/L, respectively. Bioactivity assay in vitro revealed that both rFIP-gap1 and rFIP-gap2 could agglutinate mouse, sheep, and human red blood cells. Besides, rFIP-gap1 and rFIP-gap2 obviously stimulated the proliferation of mouse splenocytes and enhanced IL-2 and IFN-γ release. Cytotoxicity detection indicated that IC of rFIP-gap1 towards A549 and HeLa cancer cells were 29.89 and 8.34 μg/mL, respectively, whereas IC of rFIP-gap2 to the same cancer cells were 60.92 and 41.05 μg/mL, respectively. Taken together, novel FIP gaps were cloned and functionally expressed in P. pastoris, which can serve as feasible and stable resources of rFIP gaps for further studies and potential applications.

Petroleum not only benefits the world economy but also contaminates the soil. In order to select the plants tolerant to petroleum, the physiological response of two petroleum tolerant-contrasting plants, Mirabilis jalapa and Orychophragmus violace, were investigated in variation of petroleum-contaminated soils (0, 5, 10, 20, and 40 g petroleum per kg soil) for 120 d. Petroleum degradation rate, seeds germination rate, free proline, and superoxide dismutase and peroxidase activities of M. jalapa were higher than that of O. violace under petroleum stress. However, the decrease rate of soluble protein, plant height, chlorophyll, and root fresh weight was greater in O. violace as compared to M. jalapa. Pearson correlation coefficient analysis was conducted, which indicated that the higher tolerance of M. jalapa was correlated with the higher level of free proline and antioxidative enzyme activities. Besides, the 10 g petroleum per kg soil may be appropriate for petroleum-tolerant plants selection, in which petroleum significantly restrain growth in O. violace but not in M. jalapa.

Due to the importance of maize as an agricultural crop and its stature as an ideal model plant for the study of developmental biology in monocots, it is natural that research into its genetic structure has gained worldwide attention. Unfortunately, although much progress has been made in our understanding of the genetic control of the maize spikelet over the last decade, the depth of research in this field still lags behind that of dicots. Here, we review the developmental features of the maize spikelet and the characterization and function of MADS-box genes with the hope of stimulating further research in this area.

No abstract

No abstract

Methyl jasmonate (MeJA) is a lipid-derived plant hormone that mediates diverse biological phenomena. Application of MeJA onto rice spikelet could exhibit abnormal floral organ development. Although jasmonic acid (JA) has been proved to be involved in maize tassel sex determination process, the roles of JA and its precursor MeJA in maize tassel development still remain obscure. In this study, we found that tassel development was decelerated by application of 2 mM MeJA. Exogenous MeJA also influenced the number of palea and stamens of tassel spikelets. Exogenous MeJA increased the expression level of some key regulator genes, which may responsible for the phenotypic change in MeJA-treated tassel, and may mediate the crosstalk between MeJA and other hormones.