title: A shrunken-2 transgene increases maize yield by acting in maternal tissues to increase the frequency of seed development.
abstract: The maize (Zea mays) shrunken-2 (Sh2) gene encodes the large subunit of the rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase. Expression of a transgenic form of the enzyme with enhanced heat stability and reduced phosphate inhibition increased maize yield up to 64%. The extent of the yield increase is dependent on temperatures during the first 4 d post pollination, and yield is increased if average daily high temperatures exceed 33 °C. As found in wheat (Triticum aestivum) and rice (Oryza sativa), this transgene increases maize yield by increasing seed number. This result was surprising, since an entire series of historic observations at the whole-plant, enzyme, gene, and physiological levels pointed to Sh2 playing an important role only in the endosperm. Here, we present several lines of evidence that lead to the conclusion that the Sh2 transgene functions in maternal tissue to increase seed number and, in turn, yield. Furthermore, the transgene does not increase ovary number; rather, it increases the probability that a seed will develop. Surprisingly, the number of fully developed seeds is only ∼50% of the number of ovaries in wild-type maize. This suggests that increasing the frequency of seed development is a feasible agricultural target, especially under conditions of elevated temperatures.
authors: Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611, USA. lchannah@ufl.edu
authors: L Curtis
authors: LC
authors: Hannah
authors: Brandon
authors: B
authors: Futch
authors: James
authors: J
authors: Bing
authors: Janine R
authors: JR
authors: Shaw
authors: Susan
authors: S
authors: Boehlein
authors: Jon D
authors: JD
authors: Stewart
authors: Robert
authors: R
authors: Beiriger
authors: Nikolaos
authors: N
authors: Georgelis
authors: Thomas
authors: T
authors: Greene
mesh_terms: D035264:Flowers / Q000235:genetics; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development*; D013696:Temperature; D019076:Transgenes; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development*
chemical_list: D010940:Plant Proteins; D051599:Glucose-1-Phosphate Adenylyltransferase