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MicroRNAs (miRNAs) are small molecule RNAs widely involved in responses to plant abiotic stresses. We performed small RNA sequencing of cotton anthers at four developmental stages under normal and high temperature (NT and HT, respectively) conditions to investigate the stress response characteristics of miRNA to HT. A total of 77 miRNAs, including 33 known miRNAs and 44 novel miRNAs, were identified, and 41 and 28 miRNAs were differentially expressed under NT and HT stress conditions, respectively. The sporogenous cell proliferation (SCP), meiotic phase (MP), microspore release period (MRP), and pollen maturity (PM) stages had 10 (including 12 miRNAs), four (including six miRNAs), four (including five miRNAs), and seven (including 11 miRNAs) HT stress-responsive miRNA families, respectively, which were identified after removing the changes in genotype-specific miRNAs under NT condition. Seven miRNA families (miR2949, miR167, and miR160 at the SCP stage, miR156 and miR172 at the MP stage, miR156 at the MRP stage, and miR393 and miR3476 at the PM stage), which had expression abundance of more than 10% of the total expression abundance, served as the main regulators responding to HT stress with positive or negative regulation patterns. These miRNAs orchestrated the expression of the corresponding target genes and led to different responses in the HT-tolerant and the HT-sensitive lines. The results revealed that the HT stress response of miRNAs in cotton anthers were stage-specific and differed with the development of anthers. Our study may enhance the understanding of the response of miRNAs to HT stress in cotton anthers and may clarify the mechanism of plant tolerance to HT stress.

In the present study, the intracellular regulatory pathways involved in the adrenalin-stimulated chloride secretion across T84 cells were investigated. Biphasic characteristics were observed in the Isc response to the basolateral addition of adrenalin (0.25 nM–100 μM). The biphasic response was almost abolished by removing ambient Cl − . Chloride secretion was found to depend on the activities of basolaterally located Na + -K + -2Cl − cotransporters and K + channels. The α-adrenoceptor antagonist phentolamine did not have any effect on either phase of adrenalin-induced Isc, while after pretreatment of the β-adrenoceptor antagonist propranolol, the adrenalin-induced Isc was substantially abolished, suggesting the biphasic response may be mediated by the β-adrenoceptor. Under whole cell patch-clamp conditions, T84 cells responded to adrenalin with a rise in inward current. The current, which exhibited a linear I–V relationship and time- and voltage-independent characteristics, was inhibited by the chloride channel blocker DPC and the reverse potential was close to the equilibrium potential for Cl − (0 mV), implying that the current was Cl − selective. When preloaded with a Ca 2+ -chelating agent, BAPTA/AM did not affect the Isc response to adrenalin, whereas the Isc was destroyed by pretreating the cells with an adenyl cyclase inhibitor, MDL12330A. These observations were further supported by the intracellular [cAMP] measurement experiment, indicating that adrenalin induced chloride secretion could be mediated by a beta-adrenoceptor only involving cAMP as an intracellular second messenger.

TMT (trimethyltin chloride), an organotin, is ubiquitous in the environment. The consumption of contaminated food may cause exposure of the human diet to this toxic compound. The present study was to investigate the effects of TMT on the regulation of ion transport across the rat distal colon. The rat colonic mucosa was mounted in Ussing chambers. The effects of TMT were assessed using the Isc (short-circuit current). Both apical and basolateral TMT induced, dose-dependently, an increase in Isc, which was due to a stimulation of Cl- secretion as measured using ion substitution experiments and pharmacological manoeuvres. The secretion was also inhibited by several K+ channel blockers administrated at the basolateral side. When the apical side was permeabilized by nystatin, the TMT-induced K+ conductance was effectively blocked by tetrapentylammonium, a Ca2+-sensitive K+ channel blocker. The response of TMT was sensitive to the basolateral Ca2+ and the intracellular Ca2+ store, which could be disclosed by applying the inhibitors of ryanodine receptors and inositol 1,4,5-trisphosphate receptors. In conclusion, TMT led to Cl- secretion, which was essentially regulated by basolateral Ca2+-sensitive K+ channels. These results suggest the importance of K+ channels in the toxicity hazard of TMT.