Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112 Page 113 Page 114 Page 115 Page 116 Page 117 Page 118 Page 119 Page 120 Page 121 Page 122 Page 123 Page 124 Page 125 Page 126 Page 127 Page 128 Page 129 Page 130 Page 131 Page 132 Page 133 Page 134 Page 135 Page 136 Page 137 Page 138 Page 139 Page 140 Page 141 Page 142 Page 143 Page 144 Page 145 Page 146 Page 147 Page 148116 / SEEDWORLD.COM DECEMBER 2016 WE CAN TELL when plants need water: their leaves droop and they start to look dry. But what’s happening on a molecular level? Scientists at the Salk Institute have made a leap forward in answering that question, which could be critical to helping agriculture adapt to drought and other climate-related stressors. The new research suggests that in the face of environmental hardship, plants employ a small group of proteins that act as conductors to manage their complex responses to stress. The results may help in developing new technologies to opti- mize water use in plants. “A plant’s response to a stressor is a highly complex process at the molecular level, with hundreds of genes involved,” says Joseph Ecker, a Howard Hughes Medical Institute Investigator, professor and director of Salk’s Genomic Analysis Laboratory. “We’ve discovered key con- ductors in this molecular symphony, which may offer clues to helping plants better tolerate stressors such as drought in the face of climate change. If you can control one of these conductors, you control all of the genes that follow its lead.” Just as humans have hormones that help us cope with threats, plants have a few key hormones that allow them to respond to stressors in their environment. One of these is abscisic acid (ABA), a plant hormone involved in seed develop- ment and water optimization. When water is scarce or salinity is high, roots and leaves produce ABA. Although the hormone is understood to impact a plant’s stress response, scientists have known very little about what happens globally after it is released. “Just a few dozen regulatory proteins dictate the expression of hundreds if not thousands of genes,” says Liang Song, a research associate in Salk’s Plant Biology Laboratory. “By understanding what those master regulators are and how they work, we can better understand, and potentially modulate, the stress response.” In their study, the Salk team tracked real-time changes in plant genetic activity in response to ABA and identified a hand- ful of these master proteins that govern responses to a wide range of external stressors, including drought. Using a tech- nique that maps where these regulatory proteins bind to DNA, the team defined key factors that coordinate gene expres- sion, allowing for an efficient cellular response to changing conditions. The Salk team focused on candidate regulatory proteins known to respond to ABA. They exposed three-day-old seedlings of Arabidopsis thaliana to abscisic acid and checked gene expres- sion at regular time points over 60 hours. In the process, they amassed 122 datasets involving 33,602 genes, 3,061 of which MOLECULAR CONDUCTORS HELP PLANTS RESPOND TO DROUGHT Scientists find key players in complex plant response to stress, offering clues to coping with drier conditions. Salk Institute were expressed at differing levels. Analysis of the data revealed a hierarchy of control, with some regulatory proteins ranking as top contributors to gene expression. Intriguingly, a snapshot of protein binding patterns at a particular time point can largely explain gene expression over a large span of time. Together, these dynamics suggest a coordinated genome- wide response to environmental triggers. “We can see that some of these com- ponents are targeted by the same master regulator proteins, which suggests precise and coordinated genetic control,” says Song. “This could be important for agri- cultural purposes because regulating one gene could in turn stimulate or suppress another whole set of genes, allowing for a comprehensive design of interventions.” The results mirror a 2013 study by the Ecker lab on the plant hormone ethylene, suggesting that such coordinated and hierarchical control of genetic activity may be common to flowering plants. SW Shao-shan Carol Huang, Joseph Ecker and Liang Song.