JIA-2019-11

2468 XU Bing-qin et al. Journal of Integrative Agriculture 2019, 18(11): 2457–2471 different varieties may have different drought tolerance mechanisms, and even the same variety may have different drought tolerance mechanisms at different growth stages. 4.1. Chlorophyll metabolism changes in two genotypes under drought stress Drought stress can result in dehydration stress in plant leaves and reduce subsequent plant growth by hindering many physiological processes in foxtail millet. Drought stress leads to a significant inhibition of photosynthesis, which arises by a decrease in photosynthetic pigments and components (Anjum et al . 2003). In this report, the total chlorophyll contents were dramatically decreased, and the transcriptomic studies revealed that drought stress inhibited the chlorophyll biosynthesis process, especially Chl a , through suppressing the activity of key enzymes which play a vital role in Chl a synthesis process, such as GSA, PBGD, and DVR (Hörtensteiner and Kräutler 2011). Moreover, the activity of PAO, as a key chlorophyll catabolic enzyme, was enhanced by drought stress. In addition, other photosynthesis-related genes, those involving PSII, photosynthetic electron transport, and photosynthesis-antenna proteins, were significantly down-regulated by drought stress. 4.2. ROS system changes in two genotypes under drought stress ROS is a universal response of plants as a defense Fig. 8 The biosynthesis and signal transduction pathways of abscisic acid (ABA) and jasmonic acid (JA). A, ABA metabolic and signal pathway and in osmotic-stress foxtail millet leaves. B, JA metabolic and signal pathway in osmotic-stress. ZEP, zeaxanthin epoxidase; NCED, 9- cis -epoxycarotenoid dioxygenase; AAO, aldehyde oxidase; PYR1, protein pyrabactin resistance 1; PP2Cs, protein phosphatase 2C; SnRK2s, serine/threonine-protein kinase; ABFs, abscisic acid-insensitive; 13HPOD, 13(S)-hydroperoxylinoleic acid; 12,13-EOT, 12,13-epoxy-octadecatrienoic acid; AOS, allene oxide synthase; cis -OPDA, cis -(+)-12-oxophytodienoic acid; OPR, 12-oxo-phytodienoic acid reductase; JAZ, jasmonatezim domain protein. DM, Damaomao; HN, Hongnian. −10 −5 0 5 Log 2 FC B 13HPOD AOS 12,13-EOT AOS cis -OPDA α-Linolenic acid cis -OPDA OPR Biosynthesis Signaling JA JA-lle Choroplast Nucleus Peroxisome JAZ MYC JA responsed genes 2.21 1.47 0.00 2.86 1.71 1.26 2.88 4.85 0.00 1.16 1.41 0.00 DM HN Biosynthesis Zeaxanthin Violaxanthin Xanthoxin NCED Chloroplast DM HN −10.40 −2.95 0.00 1.26 1.30 −1.30 4.28 3.81 4.38 4.15 3.56 7.90 AAO ABA Cytosol Signaling ZE P PY R1 PP2Cs SnRK2s ABFs 2.50 4.55 3.17 2.15 2.59 4.79 5.09 −1.29 2.98 1.53 2.18 3.02 0.00 0.00 0.00 3.22 4.90 5.24 2.67 2.96 6.09 5.36 1.98 3.75 1.29 4.27 4.78 2.46 1.04 −2.62 −1.17 0.00 0.00 2.62 1.93 −1.03 2.40 2.73 1.31 1.63 2.83 1.24 0.00 0.00 2.60 2.44 3.12 1.87 2.44 1.51 1.33 0.00 2.46 −1.03 A Table 3 List of water deficiency responsive genes involved in foxtail millet soluble sugar metabolism Gene ID Putative function Log 2 FC DM2/DM1 HN2/HN1 Gene33335 Sucrose synthase 2 –2.00 –1.41 Gene33735 Sucrose synthase 4 2.30 2.62 Gene3399 Trehalose-phosphate phosphatase 4 1.56 1.49 Gene33438 Trehalose-phosphate phosphatase 9 1.78 3.01