HHP1 (heptahelical protein 1), a protein with a predicted seven transmembrane domain structure homologous to adiponectin receptors (AdipoRs) and membrane progestin receptors (mPRs), has been characterized. Expression of HHP1 was increased in response to abscisic acid (ABA) and salt/osmotic stress as shown by quantitative real-time PCR and HHP1 promoter-controlled GUS activity. The HHP1 T-DNA insertion mutant (hhp1-1) showed a higher sensitivity to ABA and osmotic stress than the wild-type (WT), as revealed by the germination rate and post-germination growth rate. The induced expression of stress-responsive genes (RD29A, RD29B, ADH1, KIN1, COR15A, and COR47) was more sensitive to exogenous ABA and osmotic stress in hhp1-1 than in the WT. The hypersensitivity in the hhp1-1 mutant was reversed in the complementation mutant of HHP1 expressing the HHP1 gene. The data suggest that the mutation of HHP1 renders plants hypersensitive to ABA and osmotic stress and HHP1 might be a negative regulator in ABA and osmotic signalling.

Heptahelical protein 1 (HHP1) is a negative regulator in abscisic acid (ABA) and osmotic signalling in Arabidopsis. The physiological role of HHP1 was further investigated in this study using transgenic and knock-out plants. In HHP1::GUS transgenic mutants, GUS activity was found to be mainly expressed in the roots, vasculature, stomata, hydathodes, adhesion zones, and connection sites between septa and seeds, regions in which the regulation of turgor pressure is crucial. By measuring transpiration rate and stomatal closure, it was shown that the guard cells in the hhp1-1 mutant had a decreased sensitivity to drought and ABA stress compared with the WT or the c-hhp1-1 mutant, a complementation mutant of HHP1 expressing the HHP1 gene. The N-terminal fragment (amino acids 1–96) of HHP1 was found to interact with the transcription factor inducer of CBF expression-1 (ICE1) in yeast two-hybrid and bimolecular fluorescence complementation (BiFC) studies. The hhp1-1 mutant grown in soil showed hypersensitivity to cold stress with limited watering. The expression of two ICE1-regulated genes (CBF3 and MYB15) and several other cold stress-responsive genes (RD29A, KIN1, COR15A, and COR47) was less sensitive to cold stress in the hhp1-1 mutant than in the WT. These data suggest that HHP1 may function in the cross-talk between cold and osmotic signalling.

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In this paper, we report a miniature thermal energy harvester with a novel magnetic-piezoelectric design. The harvester consists of a soft magnetic Gd cantilever beam, a piezoelectric PZT sheet, an NdFeB hard magnet, silicon clamps, and a silicon frame. In this design, the harvester is driven by a temperature difference between a cold side and room temperature ambient air, unlike other magnetic-piezoelectric thermal energy harvesters that are driven by a temperature difference between a cold side and a hot side or between two hot sides. Experimental results show that with a temperature difference of 20 °C (cold side: 6.7 °C, higher temperature side: 26.7 °C), the harvester produces a maximum peak-to-peak voltage of 37 mV and root-mean square voltage of 1.98 mV. The estimated maximum instantaneous power density and average power density is 21.7 nW/cm 3 and 62.9 pW/cm 3 , respectively. Moreover, the total volume of our harvester (length×width×height: 6×3.5×3 mm) is 217 times smaller than that of previous experimental harvesters and 38 times smaller than that of previous theoretical-modeled harvesters. Therefore, our harvester is the smallest machined magnetic-piezoelectric thermal energy harvester designed to date. These features enable our harvester to be more easily implemented and integrated with micro wireless-sensors and thereby increase more self-powered wireless-sensing applications.Index Terms-magnetic, thermomagnetic, piezoelectric, thermal, energy harvester, power generator 0018-9464 (c)

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