Plants release large amounts of volatile organic compounds (VOCs) in response to attackers. Several VOCs can serve as volatile signals to elicit defense responses in undamaged tissues and neighboring plants, but many questions about the ecological functions of VOCs remain unanswered. Tea plants are impacted by two harmful invaders, the piercing herbivore Empoasca (Matsumurasca) onukii Matsuda and the pathogen Colletotrichum fructicola. To determine the VOC signals in tea, we confirmed CsOPR3 as a marker gene and set up a rapid screening method based on a 1.51 kb CsOPR3 promoter fused with a β-glucuronidase (GUS) reporter construct (OPR3p::GUS) in Arabidopsis. Using this screening system, a terpenoid volatile (E)-nerolidol was identified as a potent signal that elicits plant defenses. The early responses triggered by (E)-nerolidol included the activation of a mitogen-activated protein kinase and WRKY, an H 2 O 2 burst, and the induction of jasmonic acid and abscisic acid signaling. The induced plants accumulated high levels of defenserelated chemicals, which possessed broad-spectrum anti-herbivore or anti-pathogen properties, and ultimately triggered resistance against Empoasca onukii and Colletotrichum fructicola in tea. We propose that these findings can supply an environmentally friendly management strategy for controlling an insect pest and a disease of tea plants.

SummaryClimate change as a consequence of increasing atmospheric CO 2 influences plant photosynthesis and transpiration. Although the involvement of stomata in plant responses to elevated CO 2 has been well established, the underlying mechanism of elevated CO 2 -induced stomatal movement remains largely unknown.We used diverse techniques, including laser scanning confocal microscopy, transmission electron microscopy, biochemical methodologies and gene silencing to investigate the signaling pathway for elevated CO 2 -induced stomatal movement in tomato (Solanum lycopersicum).Elevated CO 2 -induced stomatal closure was dependent on the production of RESPIRATORY BURST OXIDASE 1 (RBOH1)-mediated hydrogen peroxide (H 2 O 2 ) and NITRATE REDUCTASE (NR)-mediated nitric oxide (NO) in guard cells in an abscisic acid (ABA)-independent manner. Silencing of OPEN STOMATA 1 (OST1) compromised the elevated CO 2 -induced accumulation of H 2 O 2 and NO, upregulation of SLOW ANION CHANNEL ASSOCIATED 1 (SLAC1) gene expression and reduction of stomatal aperture, whereas silencing of RBOH1 or NR had no effects on the expression of OST1.Our results demonstrate that as critical signaling molecules, RBOH1-dependent H 2 O 2 and NR-dependent NO act downstream of OST1 that regulate SLAC1 expression and elevated CO 2 -induced stomatal movement. This information is crucial to deepen the understanding of CO 2 signaling pathway in guard cells.

A comparative proteomic analysis of drought-responsive proteins during grain development of two wheat varieties Kauz (strong resistance to drought stress) and Janz (sensitive to drought stress) was performed by using linear and nonlinear 2-DE and MALDI-TOF mass spectrometry technologies. Results revealed that the nonlinear 2-DE had much higher resolution than the linear 2-DE. A total of 153 differentially expressed protein spots were detected by both 2-DE maps, of which 122 protein spots were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry. The identified differential proteins were mainly involved in carbohydrate metabolism (26%), detoxification and defense (23%), and storage proteins (17%). Some key proteins demonstrated significantly different expression patterns between the two varieties. In particular, catalase isozyme 1, WD40 repeat protein, LEA and alpha-amylase inhibitors displayed an upregulated expression pattern in Kauz, whereas they were downregulated or unchanged in Janz. Small and large subunit ADP glucose pyrophosphorylase, ascorbate peroxidase and G beta-like protein were all downregulated under drought stress in Janz, but had no expression changes in Kauz. Sucrose synthase and triticin precursor showed an upregulated expression pattern under water deficits in both varieties, but their upregulation levels were much higher in Kauz than in Janz. These differentially expressed proteins could be related to the biochemical pathways for stronger drought resistance of Kauz.

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The WRKY transcription factors (TFs) play multifaceted roles in plant growth, development, and stress response. Previously, we found that SlWRKY81 negatively regulates tomato tolerance to drought; however, the mechanisms of stomatal regulation in response to drought remain largely unclear. Here, we showed that droughtinduced upregulation in the SlWRKY81 transcripts induced photoinhibition and reduced the net photosynthetic rate in tomato leaves. However, silencing SlWRKY81 alleviated those inhibitions and minimized the drought-induced damage. A timecourse of water loss showed that SlWRKY81 silencing significantly and consistently reduced leaf water loss, suggesting a role for SlWRKY81 in stomatal movement. Further analysis using light microscopy revealed that SlWRKY81 silencing significantly decreased stomatal aperture and increased the ratio of length to width of stomata under drought. Both biochemical assay and confocal laser scanning microscopy demonstrated that drought-induced upregulation in SlWRKY81 expression inhibited the nitric oxide (NO) accumulation in the guard cells, which was attributed to the simultaneous declines in the activity of nitrate reductase (NR) and NR expression in tomato leaves. The inspection of 3-kb sequences upstream of the predicted transcriptional start site of the NR identified three copies of the core W-box (TTGACC/T) sequence in the promoter region, indicating possible targets of SlWRKY81. Taken together, these data suggest that SlWRKY81 potentially represses NR transcription and thus reduces NO accumulation to attenuate stomatal closure and subsequent drought tolerance. These findings provide an improved understanding of the mechanism of WRKY-induced regulation of stomatal closure, which can be exploited in the future to enhance drought tolerance in crops. | INTRODUCTIONPlant growth, development, and productivity primarily depend on water availability. Deficit water supply results in drought that remarkably affects multiple plant physiological processes, leading to yield losses (de Vries et al., 2020). Drought is a major abiotic stress, limiting crop production around the world (Bartlett et al.,