( and nutrients are transported. Du...)Researchers learn what sparks plant growth

During the last decade, Chory has made a number of significant discoveries involving a key family of plant hormones called brassinosteroids, as well as the receptors for the hormones and the genetic factors that regulate production and uptake of the hormone in the different layers of plant tissues. According to Chory, brassinolide is a potent growth hormone involved in the plant’s response to light. Such responses, which include adjusting plant growth to reach light or strengthening stems to support leaves, are central to plant survival. Brassinosteroid biosynthesis has become a critically important area of plant biology research with significant implications for commercial agriculture.

"It’s been a matter of some debate for a very long time if one of these tissue layers controls plant growth or if all three layers have to work together," Chory said. "Our paper shows very clearly that the epidermis is in control—in both driving and restricting growth. In addition, our studies show that the cells in the epidermis "talk" to the cells in the inner layers, communicating that they too should expand."

Savaldi-Goldstein made the discovery that the signal for growth originates in the epidermis by experimenting with dwarf Arabidopsis plants and the expression of brassinosteroids in the outer and inner layers of the shoot. When brassinosteroid hormone was expressed and taken up by receptors in the epidermis, dwarf plants grew to their full size. Savaldi-Goldstein and Chory also found that when a gene is expressed in the epidermis that inactivates brassinosteroid, the plant restricts growth. Thus, cell signaling began in the epidermis and followed into the inner layers of tissue, directing those cells to grow or to restrict growth.

The outer epidermis, which helps plants retain water and regulate the exchange of gases, clearly plays the role of environmental sentinel, communicating to plant tissues when co
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Source:Howard Hughes Medical Institute