The Effect of the Crosstalk between Photoperiod and Temperature on the Heading-Date in Rice

Photoperiod and temperature are two important environmental factors that influence the heading-date of rice. Although the influence of the photoperiod on heading has been extensively reported in rice, the molecular mechanism for the temperature control of heading remains unknown. This study reports an early heading mutant derived from tissue culture lines of rice and investigates the heading-date of wild type and mutant in different photoperiod and temperature treatments. The linkage analysis showed that the mutant phenotype cosegregated with the Hd1 locus. Sequencing analysis found that the mutant contained two insertions and several single-base substitutions that caused a dramatic reduction in Hd1mRNA levels compared with wild type. The expression patterns of Hd1 and Hd3a were also analyzed in different photoperiod and temperature conditions, revealing that Hd1 mRNA levels displayed similar expression patterns for different photoperiod and temperature treatments, with high expression levels at night and reduced levels in the daytime. In addition, Hd1 displayed a slightly higher expression level under long-day and low temperature conditions. Hd3a mRNA was present at a very low level under low temperature conditions regardless of the day-length. This result suggests that suppression of Hd3a expression is a principle cause of late heading under low temperature and long-day conditions

ALDH Activity Selectively Defines an Enhanced Tumor-Initiating Cell Population Relative to CD133 Expression in Human Pancreatic Adenocarcinoma

Multiple studies in recent years have identified highly tumorigenic populations of cells that drive tumor formation. These cancer stem cells (CSCs), or tumor-initiating cells (TICs), exhibit properties of normal stem cells and are associated with resistance to current therapies. As pancreatic adenocarcinoma is among the most resistant human cancers to chemo-radiation therapy, we sought to evaluate the presence of cell populations with tumor-initiating capacities in human pancreatic tumors. Understanding which pancreatic cancer cell populations possess tumor-initiating capabilities is critical to characterizing and understanding the biology of pancreatic CSCs towards therapeutic ends. cell populations were further examined for co-expression of CD44 and/or CD24. We demonstrate that unlike cell populations demonstrating low ALDH activity, as few as 100 cells enriched for high ALDH activity were capable of tumor formation, irrespective of CD133 expression. In direct xenograft tumors, the proportions of total tumor cells expressing ALDH and/or CD133 in xenograft tumors were unchanged through a minimum of two passages. We further demonstrate that ALDH expression among patients with pancreatic adenocarcinoma is heterogeneous, but the expression is constant in serial generations of individual direct xenograft tumors established from bulk human pancreatic tumors in NOD/SCID mice. phenotypes do not appear to significantly contribute to tumor formation at low numbers of inoculated tumor cells. ALDH expression broadly varies among patients with pancreatic adenocarcinoma and the apparent expression is recapitulated in serial generations of direct xenograft tumors in NOD/SCID. We have thus identified a distinct population of TICs that should lead to identification of novel targets for pancreatic cancer therapy

Enhanced Compressive Property of Al Composite Foams at Elevated Temperatures via Plasma Electrolytic Oxidation

The present work investigates the compressive property of Al matrix composite foams at different temperatures between room temperature and 200 °C. Elevated temperature results in a decreased compressive strength and energy absorption capacity of as-received Al foams. Therefore, to maintain the compressive property, the Al2O3 ceramic coating was deposited on the Al struts of the foams by the plasma electrolytic oxidation (PEO) process to form Al2O3/Al composite foams. As a consequence, the composite foams exhibit a higher compressive strength and energy absorption capacity as compared with the as-received Al foams at both room temperature and elevated temperatures because of the reinforced effect of the Al2O3 ceramic on the foam strut. The related mechanisms were explained by fractography, microstructure observation and phase composition analysis using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD)

<i>Hd1</i> expression under different photoperiods and temperatures.

<p>Leaves were harvested from 33 day old plants at the indicated times (once every 4 h for 24 h) in phytotrons, and real-time PCR was carried out for analysis of <i>Hd1</i>. M is <i>lf1132</i>; WT is Zhonghua 11.</p

Sequence analysis of <i>Hd1</i> in <i>lf1132</i> and wild type.

<p>A: The sequence differences between wild type and <i>lf1132</i>. The black triangle represents insertion; vertical lines represent single-base substitutions; blue vertical lines and numbers are relative positions in <i>hd1-3</i>. SEF and SER shown by arrows are primers to detect the 315 bp insertion. B: PCR detection of the 315 bp insertion on the <i>hd1-3</i> locus for <i>lf1132</i>. C: The expression of <i>Hd1</i> in the wild type and mutant. Leaves were harvested from 30 day old seedlings at the indicated times (once every 3 h for 24 h) in natural fields (day-length is about 14 h light and 10 h dark) and RT-PCR was carried out for the analysis of <i>Hd1</i> expression. Primer pairs HD1F and HD1R were used for the analysis of <i>Hd1</i> expression in RT-PCR. D: Deduced amino acid sequence of the Hd1 and deduced lf1132 proteins. The black line indicates the zinc-finger domain; asterisks are amino acid substitutions between the Nipponbare Hd1 protein and the deduced lf1132 protein. E: the linkage analysis of the mutant and <i>Hd1</i> locus. P₁ is Zhonghua 11; P₂ is <i>lf1132</i>.</p

The phenotype of the mutant.

<p>A: the phenotype of the mutant and wild type, M is mutant <i>lf1132</i>; WT is Zhonghua 11. B: the panicle length and internode length for mutants and wild type. 15 total plants were investigated from five repeats containing three individuals. C: The heading-date of the wild type and mutant on different sowing-dates. Wild type and mutant were planted in the CNRRI experimental field, Zhejiang province on six sowing-dates from 15, May to 21, July 2007. D: The change in photoperiod during different sowing-dates. E: The change in temperature (mean value of everyday temperature) during different sowing-dates. Red box indicates the temperature of the heading period at the last sowing-date, 21, July.</p

The heading-date of the mutant and wild type for different photoperiod and temperature treatments.

<p><i>lf1132</i> and wild type plants were planted in the CNRRI experimental fields, and two week old seedlings were transferred to phytotrons with different photoperiod and temperature treatments. The heading-date for each treatment was observed and recorded for at least 10 plants. Four phytotrons were used: LD, 27°C phytotron; LD, 23°C phytotron; SD, 27°C phytotron; SD, 23°C phytotron; A: the heading-date under different photoperiods and temperatures; B: The velocity ratio of leaf growth (VRL) for the mutant and wild type under different photoperiods (SD and LD) and temperatures (27°C, 23°C). LD treatment: 14.5 h light and 9.5 h dark; SD treatment: 11.5 h light and 12.5 h dark.</p

<i>Hd3a</i> expression under different photoperiods and temperatures.

<p>Leaves were harvested from 33 day old plants at the indicated times (once every 4 h for 24 h) in phytotrons, and real-time PCR was carried out for the analysis of <i>Hd3a</i> expression. M is <i>lf1132</i>; WT is Zhonghua 11. A, B, C, D are the <i>Hd3a</i> expression profiles under high temperature and low temperature; A: wild type under LD condition; B: wild type under SD condition; C: mutant under LD condition; D: mutant under SD condition. E and F are the <i>Hd3a</i> expression profiles for the wild type and mutant under different photoperiods at high temperature; E: wild type; F: mutant. G presents the <i>Hd3a</i> expression profile of the mutant and wild type under LD conditions.</p

The effect of different photoperiods and temperatures on heading-date.

<p>Notes: Zhonghua 11 and <i>lf1132</i> were grown in phytotrons with four different treatments. Heading-date was investigated at least 10 plants for each treatment.</p