Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 7, 2005
Publication Date: February 7, 2005
Citation: Varanasi, V., Jia, Y., Chao, W.S., Anderson, J.V., Horvath, D.P. 2005. Understanding shoot development and growth in weeds: cloning and expression of shootmeristemless from leafy spurge. [Abstract]. Weed Science Society of America. Page No. 68.
Interpretive Summary: We have cloned the gene SHOOTMERISTEMLESS (STM) from the perennial weed leafy spurge. This gene is known to be required for maintenance of the apical meristem during growth in several different plant species. However, although STM is required for meristem growth, it was unknown if it was expressed in non-growing meristems. We have shown that STM is expressed in non-growing meristems, but is significantly up-regulated with 24 hours of growth induction. We have also shown that it is inhibited in buds that are endo-dormant, but is expressed when endo-dormancy is released even in buds which are not growing due to cold temperature. The differential expression of this critical developmental regulator upon dormancy indicates that it should be suitable as a both a genetic marker for growth and as a tool for dissecting the signaling process linking development and growth of buds in weeds.
Keywords: Shoot development, Dormancy, SHOOTMERISTEMLESS, Growth
Anyone who has pulled dandelions knows that some weeds avoid eradication through the development and or maintenance of adventitious shoot meristems from root tissue. Understanding the mechanisms by which plants control the formation and growth of these meristems is critical to developing new technologies to control weeds that reproduce or survive through the generation of such meristems. However, due to a dearth of tools needed to ask fundamental questions regarding the mechanisms of meristem formation and growth, such studies have been limited to physical analysis of meristem formation. To help solve this problem, we have cloned SHOOTMERISTEMLESS (STM), a key member of the KNOTTED gene family noted for regulating the growth and development of shoot meristems. STM encodes a homeodomain containing protein. Homeodomain proteins have been implicated in body plan formation in animals and plants. STM is only expressed in a small subset of undifferentiated cells in the central zone of the shoot meristem, and is absolutely required for meristem formation in Arabidopsis. STM is responsible for proliferation of the cells in the central zone. Other KNOTTED family members are implicated in developmental processes such as bud dormancy, leaf shape and flower development in several plant species. Thus, it is not surprising that KNOTTED family genes have high levels of sequence conservation over considerable evolutionary distances. We utilized this fact to design primers capable of amplifying KNOTTED family genes from leafy spurge. An initial amplified product was cloned, sequenced, and used to isolate both genomic and cDNA clones. Several different clones (designated EeSTM1-3) were obtained, but all showed the greatest similarity to STM of Arabidopsis than to other members of the KNOTTED family. We utilized primers specific to EeSTM1 for semi-quantitative Reverse Transcription-Polymerase Chain Reaction (RT-PCR) to follow STM expression in leafy spurge. The results indicated that EeSTM1 was up-regulated within 24 hrs after growth induction in root buds of leafy spurge, marking it as the most rapidly induced gene known to play a role in shoot development following growth induction. EeSTM1 is also down regulated during initiation of endo-dormancy in the fall, but is expressed again after dormancy release by mid January.